Ok, this is most probably not a cairo bug, so feel free to close it if you're not willing to dig into this issue. However, it is an interesting effect which might - or might not - be an artefact specific to cairo.
I recently used vistaprint.de for ordering business cards for my brother and while their online preview looked correct the final printed result was wrong - the motive was cropped wrongly.
I had longer discussions with their hotline and the first one told me, that their system could not handle "layered" PDFs correctly (which is odd, because I did not use any layer features of inkscape). I tried various modifications of the PDF with their hotline, but nothing helped. The original file was generated with Cairo 1.6.4, but switching to 1.8.6 did not help, neither did help a thin line around the document boundaries apparently.
I don't like to attach these files to this bug report, since they contain personal information, however I'll put them online for a while so that anyone interested could look into them.
The files are at http://www.home.unix-ag.org/simon/vistadebug/ - the one with "Proof" imprinted on top obviously is their proof and the business cards themselves show the same weird cropping on the top and the bottom boundary.
I wonder what information in the PDF gets interpreted as the bounding box for the actual printing and what I'd have to do to work around this. For some reason it worked correctly for the left and right boundary, otherwise I'd suspect that the bounding box of the white graphics gets interpreted as a bounding box for the whole file.
Can anyone with some insight in PDF shed some light on this issue?
Many products have difficulties with pdf 1.4 (the version that cairo generates). The pdf from vistaprint is generated with PDFLib 5 which is quite old.
You can always convert your pdf file to v1.2 with the ghostscript pstopdf12 command. I get very 'compatible' results with that.
It is not clear whether the problem is vistaprint not handling pdf 1.4 or cairo generating suboptimal output. There have been many optimizations and bugfixes in the cairo pdf output since 2009 so I'm closing this bug. Please reopen if it is still a problem.