Can a patent attorney or agent not of record file papers in patent applications?

Yes, registered attorneys or agents not of record can file papers in patent applications and reexamination proceedings under 37 CFR 1.34. The MPEP states:

Filing of such papers is considered to be a representation that the attorney or agent is authorized to act in a representative capacity on behalf of applicant.

This means that by filing papers, the attorney or agent is implicitly declaring their authority to represent the applicant.

For more information on patent filing, visit: patent filing.

For more information on USPTO procedures, visit: USPTO procedures.