Version 2.5 Build 322.10, released in December 2018, is the last stable version of the Viewer.
If you're looking for free alternatives to Pdf Xchange Viewer, consider:
To activate PDF Xchange Viewer 2.5 Build 322.10 using a serial key:
PDF-XChange Viewer 2.5 Build 322.10: The End of an Era The specific version you are looking for——is the final stable release of a classic software. Released on December 15, 2018 , this build marked the end of active development for PDF-XChange Viewer as the company transitioned to its successor, the PDF-XChange Editor . Understanding Licensing and Serial Keys
: Basic viewing, annotating, and OCR (Optical Character Recognition) are completely free and do not need a license.