PDF Compression

I always scan copies of letters into my computer before I send them out. So I had a bunch of large PDF’s sitting around hogging my Dropbox space.

One day I found this blog post which claimed that simply running (in Bash) the commands
$ pdf2ps original.pdf temp.ps
$ ps2pdf temp.ps new.pdf

would decrease the file size. (The two commands are part of GhostScript, which I had installed on my Linux boxes anyways.) I couldn’t resist trying it — and miraculously, it worked. It generally decreases my scans by a factor of 10 (from 20MB to 2MB or so).

I have no clue why this works, although it probably has something to do with the fact that the PDF’s are scanned pages . Anyone care to enlighten me?

4 thoughts on “PDF Compression”

      1. Oh there’s also the issue of layering. PDF’s generated by TeX have many layers to them; using these conversions flattened the PDF’s layers, maybe?


      2. Up to now I’ve been doing this with scans from my scanner, not TeX-generated PDF’s.

        Though I just tried it with a randomly selected LaTeX PDF (actually my write-up to IMO6) and got a factor of 2 as well. Not that compression is something I’d usually need with a text PDF.


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