i no longer do the computer invoicing.i did this for several years. i just do handwritten details on letterhead now. i do the same for job quotes. maybe old fashioned, but works for me. i had a local print shop print a batch of triplicate types. i didn't much like them-- gave them all to my grand kid for drawing paper.
If you use Microsoft Word, you can go download invoice templates and change them with fonts, images, etc. to suit yourself.
Here's a link for some examples: https://templates.office.com/en-us/Invoices