Thank you for your answers.
I checked the links and cannot find any READING of pdf, just creating.
Did I miss it?
Yes, I know, that there are command line tools for converting. I want to avoid third party software, - as we are programmers.
Such a command line tool would be e.g. the VERY OLD version of pdf-shaper (if there is no other solution).
I have my reasons to want my own code. One of it is, that the new versions of it, trouble me.
So if anybody has or know an unit for it, it would be great.