How can I garbage collect PDFs that abnormally grow with Adobe Acrobat Pro DC?

Question

Using the Adobe Acrobat Pro DC on Mac OS X El Capitan, I find that when I edit a file, it grows over time at a rate that is greater than reasonable for my edits. Presumably, there is a bug in Adobe, that is causing garbage artifacts to collect in my document. For example, I added a space to some text, and a document grew by 200K upon saving as compared to the prior version. These artifacts keep accumulating as I work on a document, I have one document that has grown by more than 1MB from 5.5MB to 6.7MB.

Is there any way to clean up these documents, so as to get closer to the original size again where the size growth is abnormal? I've tried the various sanitize and cleanup tools in Adobe, but they don't seem to help, some make it worse.

Answer 1

Have you ever done a Save as… in the process?

PDF is an incremental format, which means that changes are added to the file, and the internal table to the objects is updated. This makes the file grow with every change (even if you delete all minus one pages).

With Save as…, the document gets redone, and all (well, almost all) the "dead wood" gets removed.

Another aspect is, as you say, you edited the document, that you were using a different (even just slightly different) font, which got embedded. There is the PDF Optimizer tool. You access it via menu File --> Save as other --> Optimized PDF. You may be asked to save the document to proceed. In the dialog appearing, there is the Audit Space Usage button in the top right corner. This brings up an overview of how much of the file size is used by various components, such as Content Streams or Fonts. Based on that, you may set the options in the Optimizing dialog, and save.

Note that there is one case where this method does not work, namely to get rid of no longer used fonts for form fields. When you specify a font for a form field, the whole font gets embedded (has to be, because otherwise, you can not reliably fill the field). If that font is not used anymore, it could be removed, but it is not; in this case, you go back to the blank form version, and copy over the fields. This is something you do just before you make the form available for distribution.