Mysterious pdf issue on iPad

After reading about 20 pages of data mining book in iBooks, next page rendered itself as blank. And all successive pages failed too.

When I go to arbitrary (usually blank) page, then return to library and reopen book, the page in question sometimes shows its content. But all other pages are blank as clean paper.

Oddly, there is a text on a page indeed. It's just not visible! If I use magnifier glass on a blank page, it reveals underlying text. (And no, I can't read the entire book this way:)

Some facts:

• Restarting application or ipad do not make any changes to this behaviour.


• The file renders just fine in desktop adobe reader.


• iOS 5.1.1, seems to be quite "old", but I have never encountered such issue. (Viewed at least several hundred documents)


• Pdf version is 1.4, no any extraordinary protection.

How to fix the issue, or what other things to check?