This error comes up when the document gets corrupted. If you have got the PDF from a different user, please try to re-download it and save it locally on your computer and check.
As a workaround you may also try to extract the PDF pages as a separate PDF files and then combine them together and see if that works for you
You may also get in touch with the author/creator of the PDF file and to re-create the PDF from the source file.