Why pdf plays one moment than invalid format the next

[bertrain 1]

Purchase a comic in pdf form than in couple of weeks I tried to view some of the comics most other volume is reading in valid format what a disaster so I purchased a thumb drive purchased the same comic transfer to thumb drive seemed alright few weeks later on a trip tried to play some of them volume 1 through 5, volume 2 and 3 now reads invalid format, it's like it's on a ticking time bomb,
Is there a software that format a invalid pdf format.

 

[anon(238680)]

Welcome to Android Central. There is software that will modify a pdf but not a proprietary purchased format. I would assume the files are on some kind of timer, otherwise I suggest you contact whomever you bought them from and see why they no longer work correctly.

 

[Rukbat]

Foxit MobilePDF will read just about any .pdf file (they can be formatted differently, like a web page, where a div at the bottom of the file can have CSS put that div at the top of the page). If Foxit doesn't read the file, it's not really a .pdf file. (Just having ",pdf" at the end doesn't make the file a .pdf file - it has to actually be Portable Document Format. If you can look at the raw file [with an editor like XVI32], see if it starts with %PDF-1.x [where x is the version number]. If it doesn't, regardless of what the name says, it's not a .pdf file. If it is, it can still be some proprietary format that only the comic book reader made for it can read.)

 

[Ivan Ivanenko]

I would suggest Librera Reader on Play Market. It can read many types of PDF, and some time it's better parse PDF than other readers. It's also support CBZ and CBR comic books, so you can read comics in native format.