Sometimes (I think older pdf-documents) the reader 11 asks me to save the document even if I haven't done any changes.
How can I stop this?
If they're forms, they may ask to save every time per the save protocols by the author of the form. If they're NOT forms, save them with a different name (add a dash between words) and it shouldn't prompt for a save again.
That I couldn't do. I'm a freelance web designer, not an Adobe employee. I just volunteer here. The "prevent security breaches" came from a release note I read some time back. It's generic for "we fixed some things we missed the first time" as far as I know.