Can I file certified copies of priority documents via EFS-Web?

No. Certified copies of priority documents should be submitted by mail. When a document that is required by statute to be certified must be filed, a copy, including a photocopy or facsimile transmission, of the certification is not acceptable. See 37 CFR 1.6(d)(2). An example of such a submission is a certified copy of a foreign patent application filed pursuant to 35 USC 119 or a certified copy of an international application filed pursuant to 35 USC 365. Note, however that it may be possible for the USPTO to retrieve an electronic copy of a priority document through the priority document exchange program. See 37 CFR 1.55(d).

USPTO FAQ - Questions and Answers (2007JUN01)