What is the difference between an AWS PQR and an ISO WPQR?

The quick answer is this. An AWS PQR (Procedure Qualification Record) does not include ranges of approval. These are issued to the WPS (Welding Procedure Specification). An ISO WPQR (Welding Procedure Qualification Record) includes the range of approval. An ISO WPS shall not include ranges outside the defined scope of the ISO WPQR. Lately, The abbreviation PQR is also recognized when approving a process according to ISO standards.

Most, if not all, codes and specifications require approval by the responsible engineer, welding engineer, expert, supervisor, or welding coordinator (definition depending on the applicable code/specification). The assigned expert shall have the knowledge to determine if a possible range of approval is truly the range that leads to the desired/required acceptable weld.