I have created a plug-in for Inserting a page at specified page number of a multi page PDF.
If file is a single page file, plug-in is working fine but on using with multi page pdf it is not freeing that file. (I am not able to delete that file)

Same issue I was facing while extracting words from a file but that time it was throwing an exception "releasing an unlocked object", the issue resolved by allocating and releasing WordFinder for every page.

In that case I am not getting any exception.

While same plug-in is working fine for "Acrobat 7.0".

(Most of other operations are also locking with Acrobat 8.0 while working with 7.0)