Just sharing a solution for silent printing PDFs with NativeProcess using Acrobat Wrapper by BioPDF.
If have an AIR demo and writeup at my blog: Adobe AIR NativeProcess Silent Print PDF with BioPDF's Acrobat Wrapper
This works only for Windows and there is a minor ghost appearance of Adobe Reader when printing is slow, but with a Full Screen and Always Front settings it gets the job done for now. User cannot get focus on Adobe Reader if you do not choose to overlay with Air app.
Now if I can find the same command line for MAC.
here is an article how to open and show and silent print pdf in Windows and Mac OSX with examples (using native commands):