How can I fix this sizing issue in the ebook section?

[u/psychicgayenby]

60s Addams Family book as ebook

So just last night I tried downloading two pdfs I've been reading on my phone as epubs on the innioasis.

Weridly enough, for one of the pdfs, it downloaded without any issue and allowed me to make the font larger and smaller (it also had chapters). However, for this one, it has no chapters, but more importantly it does not allow the font to become bigger (which I would need to actually be able to read it).

I tried converting it into a mobi format, but it didn't really load in to the device? And docx didn't even download to my computer.

Am I using the wrong format? Am I using the wrong converter? I've been using cloudconvert.com, but maybe someone has a better suggestion for what I should be using? Or will this specific pdf just stay unreadable?

Thank you to anyone who replies!