Problem with PDF files from web pages

[BarryL]

I have several PDF files that I created by printing web content to PDF format. With some, I receive an error that Calibre cannot open the file. This is a frequent error explanation:

Spoiler:

calibre, version 8.15.0
ERROR: Loading book failed: Failed to open the book at D:\Calibre Libraries\Bridge Library & Notes\Gerben Dirksen\Defense against Polish Club (503)\Defense against Polish Club - Gerben Dirksen.pdf. Click "Show details" for more info.

Failed to convert book: D:\Calibre Libraries\Bridge Library & Notes\Gerben Dirksen\Defense against Polish Club (503)\Defense against Polish Club - Gerben Dirksen.pdf with error:
InputFormatPlugin: PDF Input running
on D:\Calibre Libraries\Bridge Library & Notes\Gerben Dirksen\Defense against Polish Club (503)\Defense against Polish Club - Gerben Dirksen.pdf
pdftohtml log:
Page-1

Page-2

Page-3

Page-4

Page-5
Failed to run pipe worker with command: from calibre.srv.render_book import viewer_main; viewer_main()
Traceback (most recent call last):
File "runpy.py", line 198, in _run_module_as_main
File "runpy.py", line 88, in _run_code
File "site.py", line 83, in <module>
File "site.py", line 78, in main
File "site.py", line 50, in run_entry_point
File "calibre\utils\ipc\worker.py", line 194, in main
File "<string>", line 1, in <module>
File "calibre\srv\render_book.py", line 851, in viewer_main
File "calibre\srv\render_book.py", line 842, in render_for_viewer
File "calibre\srv\render_book.py", line 819, in render
File "calibre\ebooks\oeb\iterator\book.py", line 64, in extract_book
File "calibre\customize\conversion.py", line 242, in __call__
File "calibre\ebooks\conversion\plugins\pdf_input.p y", line 66, in convert
File "calibre\ebooks\pdf\reflow.py", line 1473, in __init__
File "calibre\ebooks\pdf\reflow.py", line 1871, in find_header_footer
IndexError: list index out of range

I don't know how to interpret or fix this error, or whether there is a trick to creating PDFs that can be read in Calibre. This is not a disabling error because these files will open correctly in a PDF program directly.

I'd appreciate any insights or suggestions.

[theducks]

first, try with the latest version 8.16.2
There were some issues that may include yours.

Something is blocking one of the worker processes that is needed for your type of book source.
PDF is not the best