X-plore now includes own PDF viewer for devices with Android 5.0 and up.
From mentioned version Android contains possibility for apps to render PDF into image for display. So X-plore uses this Android's functions and delivers results in its Image viewer.
X-plore doesn't contain any PDF rendering code in itself, just uses Android for this purpose. This results in nearly no increase of app size due to this function. Also the rendering is (probably) well tuned without any bugs.
The PDF viewer works only on Android 5+. Another limitation is in function set - following functions are not currently possible and not on plan to be added into X-plore: 1) searching text in PDF 2) selecting and copying text out of PDF. If you need these functions, you need to install another PDF viewer.
X-plore's PDF viewer remembers position (page) of last displayed PDF files. So when you return to already viewed document, you start in page where you left off last time.