Your PDF contains text only.. if you can get or convert it to other format, you will definitely get decent read, adjustable font size, etc.
Check some sample view / screenshot for PDF with images + tables here.
https://www.mobileread.com/forums/showthread.php?t=99064
https://www.mobileread.com/forums/showthread.php?t=98975
I had the same concern too for some PDF. But turns out those pdf are quite readable in K3. Kindle DX definitely have better viewing.