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How to compress a PDF file easily on Mac or PC: simple steps

how to reduce PDF file size

Outlines simple steps for how to compress a PDF file easily and what to do if a PDF file cannot be compressed at the first try.

PDFs are a great way to share documents across multiple platforms without worrying about how the format will look on Windows, Mac, Linux, smartphone or tablet. A disadvantage is that the size of the PDF files can be considerably larger than with a comparable Microsoft Word or standard text document. However, there are ways to make PDFs smaller thanks to free web services and free trial software. We’ll show you how to compress PDF file size.

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PDF files often reach a size that makes it impossible to send via e-mail. In that case, you can follow these steps for how to compress the size of a pdf file so that it can be easily sent by email.

When you have scanned your documents, you can actually decide how big they will be. But sometimes you forget that. Or you get PDFs from others and they are just way too big for you to send on via email. In that case, you can reduce a PDF. With a couple of steps you can load these files again and compress them.

If a PDF is too big, it’s almost never because it contains too much text. Most of the time, it is the graphics that are included. Many users scan pages or design images and then save them in their original size, even though they appear much smaller in the PDF. The inserted files still take up the space and the result is PDFs that have to be reduced in size later because they are too big for e-mails. Knowing this does not help you if you have to compress an existing PDF file.

You need the following if you want to reduce a PDF:

Any program that can be used to display and print a PDF. Your computer will likely already have a ‘print to PDF’ function or program installed, but otherwise there are several fee options such as PDF-XChange Viewer or PDFCreator .
The PDFCreator is a “PDF printer driver”. It accepts the print commands from programs and instead of printing them, he makes new PDF files from them. In the process you can also specify that he should reduce the PDF.

How to compress a PDF file easily

The process by which you can shrink your PDF is as follows: First you open the file and then you send it to the printer. But select your ‘print to PDF’ function or the PDFCreator as the chosen printer. This is set so that it compresses the graphic files when the PDF is generated and the result is a head of your PDF file – only reduced.

Steps to compress a PDF

  1. Load the PDF file into your viewer.
  2. Start printing with the key combination Ctrl + P .
  3. Select ‘print to PDF’ or ” PDFCreator ” as the printer and then click on the ” Print ” button . Don’t worry, nothing will be printed . The data is only sent to the PDFCreator!
  4. As soon as the PDFCreator window pops up, select the option “ High compression ” under “ Profile ”.
  5. Then click on the ” Edit ” button on the right.
  6. In the next window you can see “output format PDF” at the top right and a ‘settings’ wrench next to the word “ output format ”. Click on it to change the settings.
  7. Another window will open in which you should select the option “JPEG (minimum) ” under “ Image compression ”. Depending on the result, several attempts may be necessary here.
  8. Confirm the new setting with a click on ” OK ” and in the previous window with a click on ” Save “.
  9. Now you are back in the output window, where you can change the file name and the directory before you click on the ” Save ” button to create a new compressed PDF file.
  10. If everything went well, the new file should be much smaller than the original file.

How to compress a PDf on Mac

  1. If you open the PDF in the Mac app Preview, select the menu “File / Export” and then the format “PDF” in the dialog to create a new PDF. 
  2. With this export, one of the standard Quartz PDF filters supplied with macOS can be selected, which changes the PDF file, for example converting it to gray tones and making it more compact.

The setting for “Reduce File Size” actually ensures small files, but with a considerable loss of quality – the result is useless. Fortunately, you can adjust the presets and create your own optimized filter.

Customize PDF filter via ColorSync utility

  1. To do this, open the ColorSync utility and click on the “Filter” section in the toolbar. You will now see all the standard quartz filters; however, these cannot be changed.
  2. Duplicate the “Reduce File Size” entry by clicking on the context menu icon on the far right in the line and then on the “Duplicate filter” menu item. 
  3. First, double-click the new entry to change the filter name to “Reduce PDF” or something similar.
  4. After our tests, the following settings have proven to be effective: For image adjustment, enter the value 144 pixels / inch in the “Resolution” field, the remaining fields must be empty.
  5. In the “Quality” pop-up menu, select the “High” entry. Under Image Compression the value of “Mode” should already be set to “JPEG” and the slider for “Quality” should be in the middle. 
  6. Close the ColorSync utility; the program will save the settings automatically.

Now you can select your new quartz filter when you export again. In our test of a 10-page Mac & i article series, the PDF shrank from 133 to 24 Mbytes: good compression with still acceptable image quality. The procedure described applies to macOS 10.13 High Sierra and also to macOS 10.12 Sierra and OS X 10.11 El Capitan.

What to do if the PDF cannot be compressed

At the beginning, you may get the surprising result that the new file is larger than the original file. That happens especially when one starts from wrong assumptions. The success of the PDF reduction largely depends on the high resolution of the embedded images in the first PDF file and how many images there are. Because sometimes it’s not the resolution of the images, but their sheer number that makes a PDF file so large. Then it doesn’t help to reduce the size of a PDF by compressing graphics .

A 200-page PDF file with an image on each page is a huge file size even if the images are actually small. In that case you have two options:

  1. You can split the PDF file into several parts, for example with the freeware tool PDF Shaper.
  2. Or you can use one of the free services where you can upload the large file for download in order to inform the recipient that the file is ready to be picked up.

In any case, it is advisable to ensure that the initial data is not too large when creating a PDF file or when scanning the original images. Pure images can always be reduced more cleanly than a finished PDF file.