Available in pre-release 3.7

In application #

To decompress a PDF in SumatraPDF:
Or:
  • open PDF document
  • right-click for context menu
  • Document > Decompress PDF

From command-line #

To decompress a PDF using SumatraPDF from command-line:
SumatraPDF clean -d foo.pdf foo-decompressed.pdf
For explanation of all flags see SumatraPDF clean.
You might want to de-compress to inspect the structure of PDF file more easily.
If a PDF file is compressed, the decompressed version should be bigger.
If a PDF is already decompressed, this will have little effect.
You can also compress PDF.