I have Ubuntu Mate and when I open a PDF in the program that comes by default -it is Atril- it reads the pdf but shows it at 50% of its normal size (very small letters), and it does not allow me to zoom it , neither with the conrol shift +, nor with the options that it has of increase in its menu (the option appears in gray, as if it were disabled). I installed another program called Evince (default of the classic Ubuntu) and it does not let me zoom and the document appears at 40%. When I open it with LibreOffice if it is possible, but I do not like to open a pdf in a "word", and I do not like that it can be edited. Does anyone know what's going on and how do I solve it, please?