I found a pdf containing all the information I need, unfortunately it is (currently) for version 1.2019.6 http://plantuml.com/guide
I'm currently using 1.2019.3, and can't upgrade because the changes to preprocessing break my project, where can I find a similar helpful PDF but for version 1.2019.3(or older versions in general)?
You'll find something interesting here:
http://pdf.plantuml.net/1.2019.3/PlantUML_Language_Reference_Guide_en.pdf
:-)
And we are interested by the issue you have with the new preprocessor. Maybe we can fix them ? So tell us more about it... Thanks