I had a similar issue with another app (Profile) using a Windows 7 Pro computer as a sort of document “server” accessed by 4 desktop PC’s. This may give you a hint.
Issue - too many devices. Modem, Firewall, passive router, wireless access point.
Solution - Upgraded internet to most extreme. Replace old modem and wireless access point by much better ISP modem which included wireless, removed hardware firewall, replaced with better internet service and better virus and spyware protection.
PC settings on desktop and some hardware.
Issue - Some timeout settings.
Solution - Sorry. Can’t remember which settings. There were several spots in OS and apps.
Issue - Some physical issues with built in latency
Solution - Replaced Software RAID 1 with Physical RAID 1 and added SCSI cables. Replaced VeloRaptor drives with Western Digital Black drives which are data centre rated. These are now offered with Western Digital Gold drives. Added more RAM. PC RAM increased from 16 GB to 24 GB. Replaced single graphics card with dual graphics card with more RAM to support three large monitors.
Hard Drive issues on desktop and “server”.
Issue - We partitioned the drives to C and D with the OS on C and data on D. Many apps did not like this and misbehaved. The worst offenders were MS Office with MS Outlook and OneNote. I am not sure how this affected the PDF apps. In the case of MS Office there are two copies of each file - save and temp. So whatever space you require for your MS Office app, you have to double it and add some. Also none of my apps liked going across the partition to access the data files. There may have been some Windows OS artifacts as well. Now I run a full clean-up every month.
Solution - Leave physical drive whole. Use physical RAID 1 mirrored. Two drives are mirrored. Add two more drives in RAID 1 mirrored as an internal copy of the data files only to facilitate drive upgrade and OS upgrade. Use App to copy the data files on a periodic basis, usually daily.
Issue - C drive was provisioned too small and started causing issues when 80% full or more.
Solution - Double or more your estimated drive requirement. Less costly in the long run than upgrading drives later, reconfiguring apps, and moving data. I increased my my previous 750 GB drives with 2TB drives. Next time I will buy 5TB or 8TB drives.