Problem - chrome mobile shows blank grey pdf because it opens with default default Drive viewer or even Google pdf viewer.
Solution -
Install Adobe pdf viewer or any other pdf viewer. Then download any pdf.
Then go to DOWNLOADS by clicking top 3 dots in chromeh.
Then when you click the pdf, it'll ask from which pdf viewer should you want to open.
(this will work first time after installation if you haven't set any app as default viewer yet. But if you've already set & you want to change then that it should work after clearing SET AS DEFAULT setting in that particular viewer app ).
Choose your pdf viewer & you may set it to ALWAYS when meesage pops up to chhose either one time or always.
