How can i create a Letterhead into a fill in the blank PDF?
I am not sure what you mean? Are you attempting to fill in a Form field with a different Letterhead for each document?
No, i have designed letterhead by illustartor i want create pdf file from this design and make it a fill the blank PDF
Than you do want to make a PDF Form
Illy > Save As PDF
Acrobat > Forms > Add or Edit Fields
Drag a Text Field into the area
Europe, Middle East and Africa