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I have a PDF file which was saved from Photoshop, that I need to edit. File size is 30 MB.

It opens in Photoshop directly, without an Import prompt window, so it was probably saved from Photoshop originally.

Then, after all the edits, I merge visible layers, so that the file would have roughly the same amount of information as before.

After it was saved, file size increased to 150MB, 5 times the original size. Why? I haven't used "Save As" command so shouldn't it be saved with original settings and have roughly same size?

To add:
I compared the initial file and the edited file dimensions in mm, DPI and pixel dimensions, with Pitstop Inspect tool - they are the EXACT same! The only thing which was changed is "Compressed file size" went from 19% to 37% of original size - what's up with that? What compression level does Photoshop use on regular "Save" command, how do I see/change it?

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  • You are asking to compare 2 things without telling us any details about them. What modifications did you do? What is the resolution before and after? Color Mode? Size? You say it was saved from Photoshop, then that you assume it was saved from Photoshop because it opened with it; this is your OS' preferences, not Photoshop's. What are the non-visible layers? They are still part of the file even if you don't make them visible. Was there layers before? Did you keep it editable in Photoshop? Did you check if it's not a vector file to begin with? Help us help you... – BenoitLussier May 2 '18 at 13:20
  • No its not a potential duplicate. I didn't change any settings. I merged down the layers so the document has exactly one layer, same as it did when I opened it. No invisible layers. Fully raster, no vectors. Size 430x600mm, 300 DPI. "this is your OS' preferences" - this doesn't make any sense, what kind of OS preferences are you talking about? "Did you keep it editable in Photoshop?" - this option is only available if you use "Save As", which I did not use, I used "Save" – Shajirr May 3 '18 at 6:16
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This is a random stab in the dark....

If the original PDF contained data such as vector paths, live type, etc. Then that was all retained in the original PDF.

If that original was generated via Photoshop, you're correct, you may not see the "rasterization" prompt upon opening the file. Photoshop automatically rasterizes everything. You only see the prompt when the data is not Photoshop-native. The prompt is really more of a warning when opening a PDF which will result in rasterization and the original application is not Photoshop or if the PDF contains a majority of vector/live type data.

So... it's possible your original PDF contained vector data or live type data which is typically smaller than pixel data. By rasterizing everything, you've reduced it all down to pixels which traditionally take up more space (bytes) than other forms of data.

The only way to know for certain would be to examine the original PDF to see exactly what type of data existed. You can often get a better idea by opening the PDF with Illustrator since Illustrator will retain any vector or live type data when possible.

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  • "If the original PDF contained data such as vector paths, live type, etc. Then that was all retained in the original PDF. " - it doesn't, I checked in Acorbat Pro beforehand. "So... it's possible your original PDF contained vector data or live type data which is typically smaller than pixel data." - again, it does not. I just opened it in Illustrator as you suggested - it contains one raster image, nothing else. No vectors. – Shajirr May 3 '18 at 6:17
  • I found out the difference between the files - Pitstop inspect shows that compressed file size went from 19% of original to 37% - how do I change what compression level is used on "Save" command? – Shajirr May 3 '18 at 6:46

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