I have purchased adobe acrobat 9 and have my serial number how do I use that online

​Hi @Imaginative_videob2d4 ,

Hope you are doing well, and thanks for reaching out.

Acrobat 9 reached official end of support back on June 26, 2013, per Adobe's own policy, meaning Adobe no longer provides technical support, updates, or activation assistance for it: End of support | Reader 9 and Acrobat 9 (and earlier)

It's also, separately from the support issue, a standalone desktop program (Windows or Mac only) from before Adobe had any cloud accounts, mobile apps, or online activation, the way things work today. So an Acrobat 9 serial number has no connection to Acrobat Reader Mobile, Adobe cloud storage, or any Adobe ID-based service.

To point you in the right direction, it would help to know: are you trying to reinstall and use Acrobat 9 itself on an old computer you still have, or are you actually trying to unlock premium PDF editing features on your phone or tablet through the Acrobat Reader app (where you posted this)? Those are two completely different things.

If it's the second one (editing on phone/tablet today), the old serial number won't help; current premium features require an active Adobe subscription tied to an Adobe ID, purchased through the app itself or at https://adobe.ly/4h0A0Bd, unrelated to any old perpetual license.

If it's the first one (still trying to use Acrobat 9 itself), it may still install on an old Windows or Mac machine, but activation isn't guaranteed to succeed since it's long past the end of support and was never tested on modern operating systems.

Hope this information will help. 

Regards
Amal