We initially accepted the premise from IBM that OnDemand could load any file, including PDFs, up to 4 Gb in OnDemand 8.4.0.3.
Then it turned out that this version does not handle common resources in PDF separately, so it produces an output PDF with all common resources added back to each elemental PDF in the container PDF. This increased the size of our PDFs by a factor of 10 to 16, from about 32 Mb on input to anywhere from 300 to over 500 Mb on output. This was with a 1900 page internal limit to get consistent successful loads on our test system.
Once we went to production, we had a 75% "unsuccessful load" rate. The files seemes to load, but we were not quite sure. Then we came upon documentation that stated PDFs should be no larger than 50 Mb, but that with a special object parameter setting, they could be processed up to 256 Mb.
We cut the max page limit to 950 pages, and the load success rate jumped to 75% from 25%.
We then further cut the max page limit to 400, and we now get 100% of files loading on our production system without errors of any kind. With leads to files sizes that max out at about 9 Mb. That's nine megabytes, in case you think I might have a typo.
Our daily bill runs of 40,000 to 70,000 accounts will now be producing from about 300 to 700 files daily. The processing is also faster with many smaller files, going from nearly 5 hours to about 90 minutes total end to end processing of the same amount of data.