I saved couple of pdfs when I relized that the scale I set is not the scale that shows, everything is a bit bigger.
I tried to check it not only at the print composer, but in the "work space" and it is wrong there too. The project is in WGS 84 / Pseudo Mercator, and I wanted to export some google satellite images, its CRS is also WGS 84 / Pseudo Mercator.
I tried to open it with a project in WGS 84, layer set in WGS 84, but then the scale shows something like 1:119 946 154 when it should be around 1:2000... what to do?! I am pretty new to qgis (and gis, in general), please help me figure this out.