What level of .pdf compatibility does CorelDraw X6 have?

Having trouble finding any documentation on what version it supports for importing files. Funnily enough I have a file exported from Adobe CC 2015 (A MAC) using PDF Library 15.0 and it's pdf version 1.4 (Acrobat 5.x)

When I import this file into CorelDraw it ruins certain parts of the fonts (they are embedded...)
The one thing I did find online was that X6 is supposedly compatible with PDF/A archive format, ironically after converting my .pdf file to that format PDF/A it says it's completely corrupted and won't import at all!

On a side note can anyone explain why it is that when I import a file with embedded fonts that it ruins parts of the font (removes letters, apostrophes etc.) when the letters were completely available in the file and it is all being converted to curves anyway!? Makes my blood boil.