Does the problem happen with all of the PDF documents that you have? Have you tried opening the same PDF document in the desktop version of Adobe Reader on your Windows or Mac computer? (This will tell you whether the problem happens in Adobe Reader for iOS only.)
What is the version of Adobe Reader for iOS on your iPad 2?
If the problem happens with the particular PDF document in Adobe Reader for iOS, we can inspect it to determine the cause of the problem.
Would you send the PDF document as an email attachment to adobereader-ios@adobe.com? Please include the link to this forum post (https://forums.adobe.com/thread/1527268) in your email message for reference.
Thank you!