To be honest, I am not convinced this is an Okular issue, or even a poppler issue, but please reassign as needed. Example of a PDF with issues: https://digibug.ugr.es/bitstream/handle/10481/47611/26750600.pdf?sequence=6&isAllowed=y The document shows perfectly fine at Debian 10, as you can see at the attached screenshot (debian10.png) However at Debian Testing (despite the system information "Debian Release" field, that's Testing, not Sid), some characters are not rendering, and they show as empty spaces (see the debiantesting.png screenshot). As an ugly workaround (I suspected the fonts being used could be the issue) and since this Debian Testing is just a VM for tests, I removed: /usr/share/fonts/opentype/urw-base35/ /usr/share/fonts/X11/Type1/ /usr/share/fonts/type1/gsfonts/ Reloaded Okular, and at that moment the fonts used were the same as in Debian 10 (see debiantesting-fixed.png), and the characters rendered correctly. I reported the same problem at openSUSE, as I can see a similar regression at the next Leap 15.4, when I compare it with Leap 15.3 (https://bugzilla.opensuse.org/show_bug.cgi?id=1195015). The difference is that the problematic characters are shown as rectangles instead of empty spaces. Maybe relevant as well: https://bugzilla.opensuse.org/show_bug.cgi?id=1192774 https://gitlab.freedesktop.org/poppler/poppler/-/issues/1174