This is a "brainstorming" question. In fact, my brain feels like it is having a thunderstorm just thinking about it.
Consider there are two computers. One is an XP computer running 1 GB of RAM. The other runs Windows 8.1 update 1 and 8 GB of RAM.
The exact same program is run on both computers. The exact same data files are available on both computers. All application software settings are exactly the same. All application files ( .dlls, .exes, .dbf and .fpt files) are exactly the same !
A report is created in View mode ( rPreview ). The option is selected to send the report as a PDF via email. The report is 4 pages long.
The XP creates a 2 MB PDF and sends it.
The Window 8.1 creates an identical PDF but it is only 215 KB.
Why ?