Send for signatures after the document has been signed to an unknow signer

i would like to send a signed document after 2 or 3 signatures have been signed to another person to sign but this person is differnt each time and i don't know who will be signing it. the only way i've figured out who to do it is print the signed pdf then scan it back in and send out.

 

is there a way to create a blank signature line for anyone to sign?