Customarily, Jewish witnesses sign their Jewish name in Hebrew, and if witnesses of other faiths are included, they sign the Hebraicized version of their names.
If your witnesses aren’t comfortable writing in Hebrew, consult your officiating rabbi or cantor for their practices and preferences. Here are a few possibilities:
The wedding couple may ask the officiating clergy to write the witnesses’ Hebrew or Hebraicized name and the couple can take a photo of it to send to the witnesses so they can practice.
Some clergy will invite the witness to place a hand on theirs as they write the witness’ Hebrew or Hebraicized name.
Some clergy will pencil in the Hebrew name and invite the witness to trace the signature in pen.
You may want to choose witnesses who can sign their names in Hebrew, and work with your rabbi or cantor to find appropriate and meaningful ways to honor other friends.
At your officiant’s discretion, you may choose to have more than two signatories witness and sign the ketubah. Some clergy may invite witnesses to include their usual signatures to the ketubah, either in addition to or in place of their name in Hebrew.
The Eternal One spoke to Moses and Aaron, saying: "This is the ritual law that the Eternal has commanded: Instruct the Israelite people to bring you a red cow without blemish, in which there is no defect and on which no yoke has been laid." - Numbers 19:1-2
Balak son of Zippor saw all that Israel had done to the Amorites. - Numbers 22:2