A good article on this: https://blog.lucafluri.ch/2017-11-21/customizing-remarkableTablet
Resolution of templates: 1404x1872
Gimp techniques for converting a pdf into a template:
- Open PDF with Gimp
- Select area, Ctrl+V + Ctrl+C to create a layer, then "Layer" > "Scale Layer" to increase it's size.
- Change "Colours" > "Shadows-Highlight" to increase the blackness of text/lines in the file.