A print-ready PFD for a flyer or posters needs to be in high resolution, whereas a lower resolution is sufficient to display the document on a screen or print it on your ink jet printer. In this case, a\u00a0reduced size PDF<\/strong>\u00a0or an optimised PDF will do. The real challenge is to reduce the file size of an existing PDF in order to comply with upload limits, for example. This can be even more challenging when you don’t have the original file or the source application.<\/p>\n There are several ways to tackle this task: The results depend not only on the selected method or compression tool but also on the content of the PDF to a considerable extent. If you don’t want to reduce just the file size but also the page size, e.g. from A4 to A5, we have put together some\u00a0information<\/a>\u00a0at the end of this article.<\/p>\n Contents<\/strong><\/p>\n <\/a><\/p>\n As a Windows user you can use two different methods to compress a PDF to reduce its file size: You can save it as a\u00a0reduced size PDF<\/a>\u00a0or as an\u00a0optimised PDF<\/a>.<\/p>\n <\/a><\/p>\n The first method is not always the best but the most obvious one: Open the PDF in Adobe Acrobat Pro DC and choose\u00a0File<\/span>\u00a0>\u00a0Save As Other: Reduced Size PDF<\/span>. (Unfortunately, this command is not available in the free Acrobat Reader. In this case, you can try\u00a0online tools<\/a>)<\/p>\n Acrobat then\u00a0automatically<\/strong>\u00a0resamples and compresses the images.\u00a0Moreover, embedded Base 14 fonts (Courier, Helvetica, Times, Symbol and Zapf Dingbats) as well as embedded subsets are removed, the document structure is compressed and invalid bookmarks and digital signatures are deleted. Subsequently, the new PDF is saved with a reduced file size. This method does not allow<\/strong> the user to influence the level of image compression or resolution.\u00a0The images are automatically reduced to 150\u00a0dpi which can result in quality loss of the image data.<\/p>\n We use a four-page InDesign document comprising multiple images, a large Illustrator graphic, a placed InDesign file, text and various fonts with an original file size of 80\u00a0MB.<\/p>\n Exported using the “Press Quality” setting, the PDF is still 13\u00a0MB large, too much to make it available online. After using\u00a0Acrobat’s on-board compression function<\/strong>, the file is still\u00a010.3 MB<\/strong> large.<\/p>\n Our conclusion: This is a quick and easy method which doesn’t always yield a satisfactory result because especially the image quality suffers. The success of this method strongly depends on the content and the previous condition of the PDF. Responses range from an enthusiastic “Wow, that’s super-small!” to a disappointed “We-eeell…”.<\/p>\n<\/div>\n <\/a><\/p>\n For the second approach, let’s take a closer look at the setting options in a PDF. What makes a PDF file large? Which factors contribute to file size? Can’t we just reduce these factors? And, which data types can we compress?<\/p>\n We can use the\u00a0Audit Space Usage<\/strong>\u00a0to get a report of the total number of bytes used for specific document elements. With the PDF opened, click\u00a0File<\/span>\u00a0>\u00a0Save as<\/span>\u00a0>\u00a0Optimized PDF<\/span>. Then click\u00a0Audit Space Usage<\/span>\u00a0in the upper right (this option is only available in the Pro version).<\/p>\n The results are displayed in bytes and as percentages of the overall file size. Depending on the content and export settings, the\u00a0document overhead<\/a>\u00a0often takes up the most space. Containing meta data, hidden layers, file attachments or data written by other applications, it is often responsible for the majority of the file size.<\/p>\n After you have identified the memory hogs, you can proceed with tackling the individual components. Compared to the first solution (Save as a reduced size PDF<\/a>), the second approach lets us influence the compression quality: We manually adjust the individual setting options of the file and save it as an optimised PDF in compressed form.<\/p>\n<\/div>\n After confirming the space usage audit, we can compress the file size of the PDF with manual setting options. We have access to six different panels that allow us to influence the compression rate and image quality. Depending on the PDF file and its application, you should carefully check each panel.<\/p>\n Practical<\/strong>:\u00a0All manual settings can be stored as a preset and named to be accessed quickly when needed.\u00a0Adobe already provides two default settings, namely\u00a0“Standard<\/strong>” which reduces the image resolution to 150 dpi among others and\u00a0“Mobile<\/strong>” with a resolution reduction to 96\u00a0dpi and some information deleted from the document overhead.<\/p>\n<\/div>\n<\/div>\n The\u00a0Images<\/strong>\u00a0panel is one of the most efficient setting options. It enables both the resolution and the type of image compression to be adjusted individually. The dialog looks similar to other Adobe file export dialogs. Every user has to decide about the desired image quality themselves.<\/p>\n If the images in the PDF are for decorative purposes only, 72\u00a0dpi are sufficient. But if they are relevant to understand the content, you should not reduce the resolution too much. You can also play around with the quality here: JPEG or JPEG2000 compression yields good results especially for photos with colour gradients. ZIP compression in contrast is suitable for large spot coloured areas. If you choose at least\u00a0Acrobat 6.0 or later\u00a0in the\u00a0Make compatible with list box, the JPEG2000 format will be added as compression type. For black-and-white images, it is best to choose JBIG2 compression which is available for a compatibility with Acrobat 5 or later.<\/p>\n Tip:<\/strong>\u00a0Play around with the “Quality” option which the JPEG and JPEG2000 compression methods offer. Often, reducing the quality will significantly shrink the file size without decreasing the resolution too much. The JPEG2000 compression also provides a loss-free option.<\/p>\n<\/div>\n You should be extremely careful when it comes to\u00a0embedded fonts<\/strong>. One of the key benefits of a PDF is that you don’t need to have any of its fonts installed on your computer to display the original layout with the original fonts on your screen. This works because the fonts are embedded in the document. By introducing subsets, Adobe has found an intelligent solution to embed only fonts that are actually needed. If a specific font is used in a short title of six different characters only (such as “images”), for example, only these six characters will be embedded in the PDF. The remaining characters of the alphabet are not needed and thus don’t take up memory space when they don’t have to.<\/p>\n If you disable font embedding, you as the originator of a PDF document can no longer control whether and how this text will be displayed on the recipient’s side. Moreover, fonts don’t use a lot of memory space which means that they are not very relevant to yield an optimum result with a reduced file size. In our example file, fonts only account for 210\u00a0bytes, or 1.5 percent, which is why we can safely neglect them.<\/p>\n Transparency can quickly bloat a document. Already a minor shadow around an image will be sampled as transparency. When flattening transparency, these areas will irreversibly be converted to vector data and rasterised data.\u00a0Generally, PDF documents created in Acrobat 5 and later support transparency. Accordingly, this dialog is greyed out in the compatibility settings of Acrobat 4.<\/p>\n Depending on the PDF file,\u00a0transparency flattening<\/strong>\u00a0might already have been performed during the export. But unfortunately, this is not as efficient as in the subsequent optimisation. The PDF\/X-3 format, for example, automatically flattens layers and transparency in high resolution.\u00a0So you may not get any storage reduction out of a subsequent transparency optimisation for the same PDF\/X-3 document since the flattening cannot be undone.<\/p>\n Note:<\/strong>\u00a0To effectively use transparency flattening in the optimisation dialog, the PDF must still contain the\u00a0native transparency<\/strong>.<\/p>\n<\/div>\n Our example PDF was saved with the “Press Quality” setting. It is 13\u00a0MB large and still contains native transparency. Now if you optimise the PDF using the transparency flattening options described here and choose\u00a0“Low Resolution<\/span>“, you will be pleased to notice that the file size has shrunk to 5.9\u00a0MB.<\/p>\n The\u00a0Discard Objects<\/strong>\u00a0panel lets you delete unused objects from the PDF. This includes embedded page thumbnails that take up storage space. In Acrobat 5 and later, thumbnails are generated dynamically when you work with the side panel. This panel enables you to discard print settings such as page scaling, a useful but storage-intensive index or bookmarks. A word of caution: These functions may well be useful, especially in PDF documents used online. So it’s important in each case to weigh whether to give priority to a reduction of the file size or to legibility and user friendliness.<\/p>\n <\/a><\/p>\n The\u00a0Discard User Data<\/strong>\u00a0panel also provides options to shrink PDF documents. This dialog box tackles the\u00a0document overhead<\/strong> which accounts for 1.85\u00a0MB or 13 percent in our example. Remove form fields or file attachments if necessary. You can also delete metadata, comments and JavaScript actions.<\/p>\n The options in the\u00a0Clean Up<\/strong>\u00a0panel allow you to remove useless items from the document. Almost none of the components you delete here have an influence on the functionality of your PDF. Since their contribution to reducing the file size is rather insignificant, they can be ignored.<\/p>\n Thanks to manual optimisation, we were able to\u00a0reduce<\/strong>\u00a0our PDF from just under\u00a013\u00a0MB to 2.8\u00a0MB<\/strong>\u00a0\u2013 with little loss in terms of image and shadow quality. The images and resolution were compressed to 150\u00a0dpi, transparency was flattened and some redundant information deleted. For comparison: Acrobat’s on-board function was able to reduce the PDF file size to a meagre 10.3\u00a0MB in the first attempt.<\/p>\n <\/a><\/p>\n The\u00a0Preview<\/strong>\u00a0is a powerful application with many useful functions. It is also a mighty compression tool to reduce the file size of a PDF document if you know how to operate it. After opening your bloated PDF, choose\u00a0File<\/span>\u00a0>\u00a0Export<\/span> to create a new and smaller PDF. Important: Enable the\u00a0Quartz PDF Filter<\/strong>\u00a0which comes with Mac OS in the next step to reduce the PDF file size and not increase it. So choose a quartz filter first and then click\u00a0Save<\/span>.\u00a0If you export the file without the filter, the PDF will become even bigger than before.<\/p>\n Quartz, the graphics engine of the Macintosh operating system, uses the PDF format as an internal graphic model and provides several quartz filters by default which you can choose in the preview when exporting documents. You can also convert the PDF file to grey scales using the “Gray Tone” filter and take some bytes off your document. The “Reduce File Size” filter obviously sounds enticing. That is exactly what we are looking for.\u00a0But the result is disappointing: Although the file size does shrink considerably, the quality loss is very visible, rendering the file useless. Therefore, we have to do some manual work first.<\/p>\n <\/a><\/p>\n To make manual adjustments, open the\u00a0ColorSync utility<\/strong>\u00a0and click\u00a0Filter<\/span> in the menu bar. Here you see the quartz filters generated by Apple which we already encountered in the Preview. Because they cannot be edited, we will create a new filter by duplicating and editing the “Reduce File Size” filter. Click the triangle on the right and choose\u00a0Duplicate Filter<\/span>.<\/p>\n The new filter appears at the bottom of the list and can be renamed with a double-click. We named the quartz filter “small file \u2013 acceptable quality” in our example. Click the triangle in front of the name to show and edit the compression options. Set the resolution e.g. to 150\u00a0dpi under Image Sampling. The fields Scale, Max. and Min. Pixels should be empty; the Quality field should be set to High. Under Image Compression, you can usually apply JPEG and good quality as preset. After you have edited your filter, close the utility. The new filter is now displayed automatically in the Preview and can be used.<\/p>\n <\/a><\/p>\n There are also various web-based tools available to compress PDFs so you don’t need to download and install a desktop application. Just upload your PDF to the website or server of the provider and after a few seconds, you can download the file again, hopefully in good quality and with a reduced file size.<\/p>\n Pros of web-based services: They provide quick access and don’t require users to install additional software applications that take up more and more memory space. But there are also disadvantages: Since you are uploading your file to an external server, there is always the risk of data leakage. What is more, you cannot always specify the type and strength of compression and thus not change the image quality for example.\u00a0We have taken a look at the most common providers and their web tools:<\/p>\n The\u00a0Ilovepdf<\/strong>\u00a0compression tool shrinks our test files by 30 percent on average and displays the result afterwards. However, this comes mostly\u00a0at the expense of the image quality<\/strong>. The user cannot make any manual settings.<\/p>\n PDFCompressor<\/strong>\u00a0starts the compression process without further prompting and displays the results in percent. Although the provider promises on its website not to “degrade the resolution” but the\u00a0quality of the images<\/strong>\u00a0suffers considerably here as well. Fortunately, the file size is nice and small.<\/p>\n SmallPDF<\/strong>\u00a0compresses only one PDF at a time. The Pro version is needed to add multiple pages and files in one step. When we tested the tool, it was surprisingly\u00a0fast<\/strong>\u00a0and\u00a0compressed less<\/strong>\u00a0than the other two providers.<\/p>\n Other compression tools such as\u00a0online2pdf.com<\/strong>\u00a0let users have a say in the compression process. They can edit settings on quality, resolution and colour mode of images. PDF2Go<\/strong>\u00a0has adopted a similar approach. It provides predefined settings to specify the compression. pdf24 Tools<\/strong>, too, offers some options to influence the compression process.<\/p>\n Overall, we could not determine a clear winner in our test because the result will always depend on the content and format of the PDF to be reduced.<\/p>\n <\/a><\/p>\n It is not always the file size that has to be adjusted. Sometimes it can be necessary to change the page format. For example, if you want to change a PDF from A4 to A5, you can use different approaches to scale down your file.<\/p>\n The “normal” way is of course to edit the source file. But if it is not available, the following suggestions should help.<\/p>\n In Acrobat DC Pro, the easiest way is to click (File<\/span>\u00a0>\u00a0Print<\/span>) >\u00a0Printer: Adobe PDF<\/span>. Then click\u00a0Page Setup<\/span>\u00a0and enter the target dimensions under\u00a0Size<\/span>\u00a0>\u00a0PostScript Custom Page Size Definition<\/span>\u00a0(148.5\u00a0mm x 210\u00a0mm for A5). Subsequently, you can create the new PDF.<\/p>\n Sometimes removing the margins already brings the desired outcome. To learn how to use Acrobat or smart web tools to crop a PDF, read our\u00a0Cropping PDFs<\/a> article.<\/p>\n Using Adobe InDesign is another option. Create a new document of the size you need, A5 in our example.\u00a0Choose the\u00a0Rectangle<\/span>\u00a0tool from the tools panel and drag it out to the desired size. Then click\u00a0File<\/span>\u00a0>\u00a0Place<\/span>\u00a0and select your PDF. Make sure that the\u00a0Show Import Options<\/span> check box is enabled before confirming the dialog.<\/p>\n In the next dialog, you can specify which pages of your PDF to import into the InDesign file.<\/p>\n As PDFs generally have more than one page, it would be rather tedious to drag out a new image frame for each single page. Scripts come in handy here and InDesign fortunately has them on board. Choose\u00a0Windows<\/span>\u00a0>\u00a0Utilities<\/span>\u00a0>\u00a0Scripts<\/span>\u00a0and double-click the\u00a0Place Multipage PDF<\/span>\u00a0script. The further process is self-explanatory. We received some error message in our test but the document was placed correctly.<\/p>\n Alternatively, you can use the Multi Page Importer script by Mike Edel. It is available for\u00a0free via Github<\/a>.<\/p>\n\n
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Compressing PDFs: Windows users<\/h2>\n
Solution 1: Saving the PDF with a reduced size<\/h3>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-save-as.jpeg\")
<\/a>Solution 2:\u00a0Compressing the PDF and saving it as a reduced PDF<\/h3>\n
![\"A](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-audit-space-usage.jpeg\")
<\/a>“Images” panel \u2013 effectively reducing image size<\/h4>\n
![\"PDF](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-image-options.jpeg\")
<\/a>The “Fonts” panel \u2013 use with care<\/h4>\n
![\"PDF](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-font-options.jpeg\")
<\/a>“Transparency” panel \u2013 save space depending on the document<\/h4>\n
![\"PDF](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-transparency-options.jpeg\")
<\/a>“Discard Objects” panel \u2013 weighing between file size and user friendliness<\/h4>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-discard-objects.jpeg\")
<\/a>“Discard User Data” panel \u2013 the document overhead<\/h4>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-discard-user-data.jpeg\")
<\/a>“Clean Up” panel \u2013 compress the document structure<\/h4>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-clean-up.jpeg\")
<\/a>Our conclusion: a promising approach to downsizing PDFs<\/h4>\n
Compressing PDFs for Mac users: the Preview<\/h2>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-mac-preview.jpeg\")
<\/a>Manual intervention: create a new quartz filter<\/h3>\n
Compressing PDFs \u2013 with and without software<\/h2>\n
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Compressing PDFs with one mouse click<\/h3>\n
Tools that enable manual settings<\/h3>\n
Compressing and scaling PDFs: adjusting the page size<\/h2>\n
![\"Screenshot](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-with-acrobat.jpg\")
<\/a>InDesign as an alternative<\/h3>\n
![\"A](\"https:\/\/www.onlineprinters.ie\/magazine\/wp-content\/uploads\/2019\/08\/compress-pdf-indesign-place-pdf.jpg\")
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