BiggerPockets

I am assuming you have already agreed to price and terms with both owners. I am also assuming you are meaning to say that this is one property owned by 2 individuals?

If the above is true then simply e-mail one owner the contract and have them sign the contract and them have that owner e-mail/fax the signed contract to the other owner. Once you have both owners sign the contract then you sign it and then make sure both owners get the completed contract sent to them for their records.
If you lack the computer/contract background or experience then a title company or closing attorney (depends on who you are using) will sometimes be glad to do the contract for you and make sure each owner signs it in the appropriate boxes including notaries, copies made and property closed. Call your title company, I almost always do mine myself, but I have been on vacation before and called my title company and they did the contract per my direction and had everyone sign it.

E-mailing pdf is a good way, but if you need a super clean copy, then yes mail is better, however you should probably include return postage and large envelopes for faster returns. Overnight cost is expensive though.

Good Luck
Big E

When it is time for closing then the sellers (owners) need to be at the closing in person, if they are then no notary required. If they can not be at the closing then yes they will need to sign, have it notarized. They call this a "mail away" closing.

If you are just having a sales contract signed and you are wholesaling the deal, then you may not need it notarized; depending on your states RE laws. Only when the final closing documents are ready do you need it notarized or have the seller there in person to sign the final contract