Sounds like a job for Rosetta tools rather than the apps. If you just want to do PDB manipulations and prepare them for Rosetta, checkout the tools directory that comes with Rosetta. Inside is two scripts for exactly what you are talking about. python tools/renumber_pdb.py and python tools/protein_tools/scripts/clean_pdb.py
Clean_pdb.py is really nice because it prepares the structure for Rosetta and can automatically pull it from the PDB if you don’t have the file.