Converting a PDF document to a PDF/A with Acrobat 11 Professional
Open your PDF and select file -> Save As -> More Options -> PDF/A
Converting a PDF document to PDF/A with Acrobat 9 Professional
Open the PDF document and select Preflight from the Advanced menu:
Under PDF/A compliance, select the 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, make PDF forms (in standard PDF format) available for filling out in a browser. If you have Acrobat 9 Professional or higher, you can save such a form, then convert it to PDF/A. However, if you have Acrobat 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 other contexts. Note that it will create a file in PDF/A-1b format that is acceptable for CM/ECF 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):