I have a set of white label PDF forms that I need to brand for our company. The initial document is 6 pages, 316KB, and already has a full set of fillable fields. In a perfect world, I just open up the first page, replace the header with a header that has our logo, save, and be on my merry way. If the file size jumps a bit, I can just go into Acrobat and "Reduce File Size."

However, the results were really bad. I think I about doubled the file size by doing this on one page alone. I thought the inflated size might have something to do with fonts since I had to "Find Fonts" in Illustrator, so I outlined my company's header (it used a different font) and went through every page to get all of the fonts on the same page. The results were worse: 2.49MB!

PDF file sizes have always felt like a dark art to me, and I want that to change. If my Photoshop file is huge, I know it's because of document dimensions, layers, and such. When my AI file sizes got out of control, I learned that unchecking "save PDF compatible version" would help out a lot. When I'm making my own PDFs and I want to export them, I have a solid grasp on downsampling and such to get a good file size.

But when it comes to editing PDFs, I really don't know how file sizes work. I don't know what "Reduce File Size" means. I don't know why sometimes a file size will double or triple and why it sometimes won't, and if PDFs are embedding duplicate data, I don't know how to get it out.

So, how do I keep file sizes down when editing PDFs?

4 Answers 4


Look around for the Audit space usage ... option (explained here). In newer versions it is oddly hidden under Save as > Optimized PDF. That will tell you exactly where the bloat is coming from. You can also use the Optimized PDF option to crank the size down in very targeted ways.

Given the big before/after shift, the culprit is probably the image you're embedding. Try exporting that file in various formats (PDF, jpg, png) and then import it.

  • Thanks for this; I'll explore. I'd like to clarify though that I didn't embed an image in this document; the logo and text are vector. I mentioned downsampling in general terms; my wording could have been better.
    – Brendan
    Nov 9, 2012 at 17:26
  • My wording could have been clearer too. Point is, whatever branding you're dropping into the file is probably causing the file size increase. Trying vector vs raster in various formats may take you in the right direction. Nov 9, 2012 at 17:32
  • Whoa! How did I not know about the PDF Optimizer feature? I'm so glad I asked. I had 96% locked up in "Piece Information"; discarding user data drastically improved the file size. Thanks!
    – Brendan
    Nov 9, 2012 at 17:36
  • 5
    It used to be a very obvious feature. If you didn't heavily use older versions of Acrobat, it's an easy thing to miss. Adobe isn't big on UX ;) Nov 9, 2012 at 17:51

You can also select whther or not to allow reading of the PDF from older versions of adobe reader or acrobat. The more backwards compatibility that you have the bigger your file will be. You should find that if you say restrict the compatibility to the latest version of adobe then the file size will be smaller than if you allow backwards compatibility to say Adobe Acrobat 4.

Its just a small thing but it may help...

  • 1
    I used to use that trick all the time. I saved most of my files down to Acrobat 4. These days it seems like a lot of the PDFs I've produced actually go up in size with backward compatibility. It's especially apparent where transparency needs to be flattened. Maybe the newer versions are doing a better job with compression. Nov 9, 2012 at 17:05

I've found out that unticking the 'Preserve Illustrator Editing Capabilities' box under the General tab gives me a smaller size pdf.

If you want to preserve Illustrator editing capabilities, you may run ACTIONS_Delete Unused Panel Items, this may help in getting a reduced file size when you save your pdf.


You can still work in Photoshop the way you do and keep a high resolution, and save your PDF without any compression.

Then you can use Adobe Acrobat Pro to have a very good control on your compression instead and adjust it for web or print-ready files.

Some info about how to compress your PDF file properly and here as well.

What makes you PDF heavy is that Photoshop and Illustrator will save invisible data such as your author data and preferences. It also does a very bad job at compressing images. The layers and editable features also increase the file size of your PDF.

Some extra details about heavy Photoshop files.

In Illustrator, the number of paths can affect the file size as well and that's very hard to optimize without cleaning up a bit your vectors. Also, when applying mask or importing images, they may not appear on your artboard but that information is still stored within the file! If you use Acrobat Pro to optmize your PDF file, it will get rid of that useless data you don't see and really crop your images.

And in general, it will equally optmize the resolution of your rasterized images.

Some tricks to optimize PDF files with a lot of paths in Illustrator and how to reduce the file size.

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