Open the PDF document, select Advanced menu, then select Preflight:

Select the dropdown for PDF/A compliance, and select Convert to PDF/A-1a option to create the PDF/A document.

Creating a PDF/A document with the “print” method

Many web sites, such as uscourts.gov and jud.ct.gov, make PDF forms (in standard PDF format) available for filling out in a browser. If you have Acrobat 9 Professional, you can save such a form, then convert it to PDF/A. However, if you have Acrobat 9 Standard instead of Professional, you must “print” it from the browser, with “Adobe PDF” selected as the “printer”.

The print option is also available in word processors, in Acrobat 9 Standard and Professional, and in other contexts. Note that it will create a file in PDF/A-1b format that is acceptable for submission, but hyperlinks (if any) will not work - so use it only if you have no other option for creating PDF/A.

Open the PDF in the browser or other application. Select the application’s Print option (often on the File menu). In the list of printers, select Adobe PDF:

Click the Properties button. On the Adobe PDF Settings tab, select one of the PDF/A1b:2005 options from the Default Settings drop-down (either option is OK). Then select the OK button: