You have two options for placing a PDF in an information field.
The PDF file is on your hard drive or computer and you need to upload it in the back office.
You uploaded it elsewhere and have the URL of the file.
Please note, documents can only be offered as a download - in other words, in the form of a URL - in the product description.
1. Upload PDF file
Go to Tools >Files in the left menu of your back office.
Click on Upload files at the top right of the screen.
A pop-up window will open where you can select the file from your computer. Add the file to the back office.