Adobe Acrobat Reader and Foxit Reader both have a feature that allows them to remember what was the last page the user was reading.
Where do these PDF readers (both Adobe and Foxit) store such information?
Most likely the registry. For instance, Foxit Reader stores that information at the following location:
Ther's a subkey for each recently opened file, and a value called
In some cases, I think this kind of data can be stored as metadata for the PDF, which is basically just key-value pairs.
In other cases it might be stored by the particular application used to open/modify the PDF (the location would then vary from application to application).