Hi DonnaS,
I think there isn't any OOB software as far as I know.
There are two options which I can let you know.
1. If the client can enter the orders you can ask them to enter using customer portal for D365 Supply Chain Management
2. You can possibly look at a solution where you can use Power Platform and AI Builder in it to scan the PDF and create a Power App use Power Automate in the solution too and make it easier for data entry
But the challenge for the second option is also you need to make sure if the customer item code and the item code which you have in the system is similar. If not you would require to have that mapped out either using Search Name (if you haven't use for any other purpose) or use the Release Product > Sell Tab > External Item description.
Thanks,
Kasun
The reply is solely my personal opinion. It doesn't reflect my employer of Microsoft opinion.
my D365 related web site link is below
D365Blog