I am unable to open pdf file saved in my iPad

Hello,

as the title says I can’t open pdf file saved in my iPad, that i could previously (yesterday) open without problems. It’s actually three files with this problem so i doubt i damaged them somehow at once, the rest from the batch works fine. It’s full of study materials with my own notes that i need right now…

When i tap on them, nothing happens, if i try to duplicate/copy/move/share them, nothing happens too. I also tried to delete them and it just said “can’t delete, file doesn’t exist”. Im pretty sure the files existed just a few hours ago… i tried restarting the iPad 3 times, nothing changes.

How can this be fixed? I can’t afford losing these files.

[Re-Titled by Moderator]