- AutoCAD doesn't take into counts a PMP file when plot is made from C# code;
Wrong. AutoCAD DOES take into account of PMP file, if the selected plotting device is presented as *.pc3, and the there is a *.pmp for it (e.g. a PMP file named the same as the PC3 file., whether the plotting started as built-in command, or from you custom code (in your plotting code, you need to set the plotting device to a PC3 file, right?).
When you use Autodesk's plotter manager UI to generate a custom plotter configuration (PC3) file (or modify an existing one), besides the generated *.pc3 file, there could also be a *.pmp file (plotter description file) generated when you specify a custom paper (size, margin...).
As I said in my previous reply, my office use a custom PC3 file for a custom paper size, specifically for our custom plotting application I wrote. As long as the *.pc3 file and the corresponding *.pmp file is available to an AutoCAD computer (that is, the 2 files are in the location specified by AutoCAD->Options->Printer Support Path->Printer Configuration File Search Path/Printer Description File Search Path), our custom plotting app does the plotting (to PDF) as expected.
Of course, in our case, we place the PC3/PMP files on a network and all users' AutoCAD's printer support path is pointed to the network location, so there is no need to distribute/install the PC3/PMP file to each computer. In a plotting app, one can have code to check the PC3/PMP availability before custom plotting starts.