FYI. New: PDF-XChange Editor Portable 6.0.322.4 (PDF editor and viewer) Released for the PA Platform, courtesy of PortableApps.com. Also: PDF-XChange Viewer Portable 2.5.322.4 (PDF viewer) Released.
Thanks for heads-up on PortableApps.com version of PDF-XChange Editor. I have been using the portable version (non-OCR) from Tracker, but PortableApps.com makes updating easier.
Sumatra for the last 10 years because of its simplicity, but I've recently taken another look at Foxit portable and found it impressive.
PDF-XChange Viewer is still being updated, latest version is 2.5.0322.5 released last month, though latest version history is from 2.5.0316.0 released January 2016: https://www.tracker-software.com/product/pdf-xchange-viewer/history
Although I prefer and use the old 6 for PDF's on Windows 8.1, on Windows 10 I am using Sumatra. One thing I cannot stand is opening PDF's in Edge. Ugh. Not only that but i'm lost trying to find how to edit/save in Edge and absolutely do not like hunting around on the new menu for favorites etc.
It has not been discontinued, despite what they claim, and is still receiving updates. It was last updated on the 27th of June. I did just download and install PDF-XChange Editor, but for now I'll continue using PDF-XChange Viewer.
It is not being actively developed for two years and it is not receiving new features or fixes. The reason why there are still updates:
For what I understood, PDF-XChange Viewer updates only update version number and installer, to keep track with PDF-XChange Editor versioning. The latest PDF-XChange Viewer content update was the mentioned version 2.5.0316.0, that resolved a vulnerability. Edit: I'm sorry, I overlooked mood's reply, that refers to a Tracker Support statement regarding PDF-XChange Viewer updates.