On 13/10/2020 19:09, LARONDE Thierry wrote: > Can you simply point me to the (u)pTeX .ch file and point me to the > initial documentations/articles that list the primitives > needed and what they have to achieve? https://tug.org/svn/texlive/trunk/Build/source/texk/web2c/eptexdir/pdfutils.ch?view=log contains I think all of the utility primitives. Quite a bit of code is devoted to setting up random numbers: it's basically a self-contained block. The other parts are actually more interesting from the point of view of integrating to other things. Joseph