Who can sign form PTO/SB/39?

The PTO/SB/39 must be signed in accordance with 37 CFR 1.14(c). Thus it must be signed by:

1. An applicant;

2. An attorney or agent of record;

3. An authorized official of an assignee of record (made of record pursuant to 37 CFR § 3.71); or

4. A registered attorney or agent named in the papers accompanying the application papers filed under 37 CFR § 1.53, or the national stage documents filed under 37 CFR § 1.495, if an executed oath or declaration pursuant to 37 CFR § 1.63 or § 1.497 has not been filed.
USPTO FAQ - Questions and Answers (21DEC2007)