Yesterday I downloaded KB1014305 which is Web Client 10.4.2 Update 4 and installed it in my development environment. Today I noticed that when opening PDF documents they don't display. I get the tool bar for the electronic file browser but the document never displays. I've tested this in Edge and Chrome with the same results.
My Web Client displays as 10.4.2.667 and the PDFs are generated by Laserfiche Forms 10.4.5.282.