ghostscript optimization improvements, PDF preprinting

Several Improvements to the PDF-processing should be tested & potentially implemented:

a) Check if the currently used ghostscript optimitzation for PDFs can be improved by adding   

-dSubsetFonts=false

 to the optimitzation. By default font-subsetting (subsetting = removing all characters, that are not used in the PDF) is enabled by using the

-dPDFSETTINGS=/screen

Option what currently is the case and potentially cause the neccessity to provide in-context fonts for the visual.

b) Implement pre-printing to solve problems with non-processable PDFs (font-forge exceptions) by utilizing LibreOffice Draw via commands to "pre-print" the PDFs at least to replace the currently used "remove all fonts" Fallback

Ghostscript doc / params:

https://ghostscript.com/docs/9.54.0/Readme.htm

https://ghostscript.com/docs/9.54.0/VectorDevices.htm#Overview