cannot open PDF file

[mosesabc]

C:>java -jar pdf-unstamper.jar -i 111.PDF -d -k "更多电子书资料请搜索「书行天下」：http://www.sxpdf.com" -s -c
[Processor] Processing PDF file '111.PDF' ...
[Processor] Error loading file '111.PDF' as PDF, skipping

[hwding]

is that a pdf file "更多电子书资料请搜索「书行天下」：http://www.sxpdf.com/"?
it seems does not contain a '.pdf' suffix, better rename the file to a simple one and retry.