To add a document to a Form, you will need to begin by adding an Upload to your Eventree event. You can find out how by seeing this help article.
Once you have uploaded your file, you can proceed with the below.
On your Form, add a Content Block. Then write whatever text you wish to appear. This text will link to the document.
2. Select the text you wish to add a link to (1), the click the hyperlink button (2). This will open up the Insert link box. In 'Url' enter the link to your upload, which is provided by Eventree. Then click Ok.
Once this is uploaded, when someone is completing a form, they can click on the linked words to load the file.