Simple Scan produces PDFs which do not conform to Adobe's published PDF specification.
Saving a document scanned with SimpleScan and saving it as PDF, then rasterizing it to png with GhostScript yields the following error:
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pngalpha -sOutputFile=
GPL Ghostscript 8.71 (2010-02-10)
Copyright (C) 2010 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
**** Warning: An error occurred while reading an XREF table.
**** The file has been damaged. This may have been caused
**** by a problem while converting or transfering the file.
**** Ghostscript will attempt to recover the data.
Processing pages 1 through 1.
**** This file had errors that were repaired or ignored.
**** Please notify the author of the software that produced this
**** file that it does not conform to Adobe's published PDF
The affected file is attached.
Ubuntu 10.10 amd64