[Turtle91]

I don’t know the exact problems with the pdf conversions without being able to see examples. However, there are a couple things I can mention that will set you looking in the right direction.

There is no automatic process that can determine links if there is nothing to indicate a link in the original document. I suspect the successful pdfs have had those links/bookmarks already created in the pdf before the conversion, the failures didn’t.

When you say the pdf conversion was almost perfect, I start to think I’m in an episode of twilight zone (did I just age myself?!?) because it’s very difficult to get a ‘decent’ conversion from a pdf, let alone a near perfect one. It might look decent but I would suspect that when you open it up in Sigil/Calibre you will find either a bunch of nauseating code, or just a bunch of images of each page, that may cause problems in different readers/apps/systems.

Tread carefully!!

Cheers!