Photoshop CS2 - PDF files help

[blueerica]

I'm crossing my fingers that someone might have an idea on why my Photoshop nearly triples the size of a layered PDF that is merely opened and closed, while when two other co-workers do the same, the size remains the same.

When saving a copy without layers and no changes, it nearly doubles the size of a file.

Any idea of what might be happening, or where I can begin looking for a solution (outside of getting Illustrator so I can start working with these files in the manner I choose)? I've checked adobe.com and did a basic google search on the problem... no one seems to mention anything like this. Perhaps I'm asking the wrong questions?

*insert hopes that someone knows WTF I am talking about*