Compressing PDF

[SkyHighRanch]

Can i compress pdfs with acrobat pro DC?

[Test Screen Name]

Sometimes. Depends what’s in them to throw away. Look under File > Save as other. 

[Dov Isaacs · Accepted solution]

To be a little more explicit, virtually all PDF files by definition are internally compressed using various techniques (including lossy JPEG and JPEG2000). Object streams including text and vector graphics are internally ZIP-compressed for PDF 1.5 and above.

Despite what anyone may claim, the vast majority of any space savings coming out of any reduced size or optimized PDF settings in Acrobat is from mucking around with the raster images within your PDF file. No raster images in you PDF file, then little if any benefits of any compression or optimization. In terms of images, there are three settings for images that can potentially reduced the amount of space required for the images within the PDF file:

(1)  Changing the image compression from a lossless format such as ZIP or lossless JPEG 2000 compression to a lossy JPEG or JPEG 2000 compression. The space saving comes from what is effectively loss of fine detail. You may or may not be able to notice the difference depending upon the image resolution and content type.

(2)  Changing the quality of lossy compression from maximum quality to lower qualities which may be very visible in the resulting PDF file.

(3)  Downsampling the images to a lower resolution. This is definitely lossy, but if your images are exceptionally high resolution (anthing over 450dpi for color or grayscale images), the results should not be a problem unless you intend to magnify the PDF either for display or printing.

Of course a combination of (1), (2), and (3) can yield signficant file size reductions, but at a potentially high loss of quality.

One thing not to do is to use any file reduction / optimization option that removes embedded fonts. You cannot assume that whoever receives your PDF files has the fonts (or the same versions of the fonts) that you have unembedded on their system. All fonts referenced (i.e. used by text) in a PDF file should be subset-embedded in PDF files.

Please remember that contrary to the “old days” when 72dpi was “sufficient” for screen display, many modern computer and mobile device screens have resolutions of 300dpi and above, surpassing the needs for high quality offset printing!!! 

The bottom line, of course is that you (or someone you are providing a PDF file to) cannot “legislate” the size of a PDF file. If there are no or very few raster images in a PDF file, there is virtually nothing you can do to cut the PDF file size other than totally cutting out some contents. Otherwise, it is a matter of how much loss of quality you are willing to endure.

[Asher@]

Is that possible to compress PDF by resizing the output PDF page size? I mean, for example, change the page size from A4 to A5? Or change the margin or crop the PDF? Can we do by these solutions to reduce the file size yet keeping the resolution of the images inside the original file?

[Test Screen Name]

No, they make it smaller on paper without removing anything in the file. Same size.

[christinahannon]

If you have the images on your pdf file try to reduce the image size and use it then check the pdf size 

[Test Screen Name]

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