Correcting or adding drawings after a patent application is filed is addressed in MPEP 608.02, subsection II. The key points are: Drawings can be corrected, revised, or added if no new matter is introduced. The applicant must submit a proposed drawing correction in reply to the Office action. For non-provisional applications, replacement sheets of corrected drawings must be submitted. For provisional applications, corrected drawings may be submitted as an amendment to the application. The MPEP states: 'Where a drawing is to be amended, applicant must submit a replacement sheet of drawings which complies with 37 CFR 1.84 and includes all of the figures appearing on the original version of the sheet, even if only one figure is being amended.' This ensures that the entire drawing set remains consistent and complete. To learn more: drawing corrections patent application amendments replacement sheets USPTO requirements