I just want to read the contents of a PDF file.
Could you confirm what is the issue while viewing the PDF? Also, provide us with a few more details.
1. Are you not able to view the contents of other PDFs too?
2. What is the OS name and version you are on?
3. What is the app version?
Make sure that it is up to date.
To find your iOS, go to Settings > General.
When the size is zero bytes, there is nothing in the file.
Adobe Acrobat Reader for Mobile is free. What are you paying for?
Adobe Acrobat Reader is one of several PDF readers. If you can't read the PDF in any PDF reader, then the issue is with the file, not with the reader. It sounds like you also tried "Easy PDF" and could not read the files there either.
Where did you get these files that you are trying to read? From the web? By email?
Also, some government agencies use LiveCycle to create the PDF. If you try to open one of those, you will get a message saying it cannot be opened on a mobile device. You didn't say you are getting that message, but it is another possibility.
The version of Acrboat Reader can also be found in Settings.