How can you have more than 1 signature to sign with?
Hope you are doing well. Per the description, you want to save more than one signature.
As designed, you can save one signature and one initial on the latest version of Acrobat Reader Mobile.
We would love to know more about your idea. Please share the idea here: https://acrobat.uservoice.com/
This ensures your idea reaches our product team to review and try to implement in the upcoming updates.