How to create one pdb file form some pdb files?

Hi all,

I need to pdb file of a protein (Tissue plasminogen activator with 527 residues). There is a full sequence of that.

This protein has 5 domains. There are 5 pdb files separately. I want to have one pdb file containing the whole of protein. What is the best way (tool or program) to do that?

Best regards,
Leila