From the File
menu, select Publish to,
Publish to PDF,
and click the Settings
button:
2
Click OK
to return to
the “Publish to PDF” screen to complete
document production.
The compatibility setting will remain
set to PDF/A until you change it.
3
Select
PDF/A-1a (preferred) or PDF/A-1b from
the "Compatibility" drop-down and click
OK: