Its PDF parser doesn't seem to support all PDFs, and for some PDFs it will PRINT, on paper, an error message from the PDF parser.
So not only did it not print a perfectly valid PDF, it also wasted paper and ink for it.
You can't know beforehand which PDFs it'll support or not from looking at them, any computer / phone PDF viewer supports those. It could be as simple as a PDF sent by an airline.
They should:
1) use a proper PDF library, not some half baked one
2) if something is wrong with the PDF, show the error on screen, not waste paper for it