I should have asked: Would you mind describing the particular use for multiple signatures? It may be that we've missed something important. Do you have multiple people, or just multiple signatures for an individual?
My use for multible signatures would be used for different "job roles". I have two roles at work where I frequently approve and sign documents. I need to sign in the two roles with a diffrent signature in each. I also sometimes sign with the whole signature and sometimes with only initials. It would be very helpful to have the option to save, maybe five, different "signatures" to use in different situations.
This would make my workflow MUCH better and faster.
It's not something we've discussed until this thread, but I will be sure your request makes it to the team that owns the signature features. It will be more likely to be implemented if others request it as well!
Another reason to want access to several signatures is that many documents require the placement of a visible signature by more than one person prior to submission of the document to the Authority that requires it. For example a nomination form for a meeting needs to be signed by the nominator and the nominee.
For these sorts of multiple-signer workflows, we suggest using a service like Adobe EchoSign.
If this is just an occasional use, you can zoom in and use the Pencil tool to have any number of people draw and resize their signatures to fit the document.