Does IBM Document Manager (DM) Rendition Services re-scale the image when it starts Adobe Acrobat via the command line to print the document?
No. Running Acrobat from the command line will not re-scale the image, even if the page scaling is set to "Fit to printable area" in the Acrobat GUI.
However, after finishing rendering the first PDF document using DM Rendition Services, the Acrobat process will not exit until the DM Rendition Services restarts. Within the same rendition service, the already existing Acrobat process will print new jobs with the Acrobat printing configuration in Acrobat GUI mode.