Hi Johnny
I have done this in the past. You can create an HTML link in your survey to the document in question. Have a look at my blog about HTML links in Survey123: https://community.esri.com/t5/arcgis-survey123-blog/html-links-for-survey123-to-just-about-anything/...
Basically you follow these steps:
1) Add the PDF or Excel file to your AGOL by going to Content / New Item / Choose to add the file from 'Your Device' or simply drag and drop the file into the area shown:
Once you have created the item you will be taken to it's item page. From there you probably want to share the file publicly to avoid any sharing issues (unless it is sensitive information).
Once shared, you can copy the link to the file by scrolling down on the Overview page of the item and copying it's URL:
In Survey123 you can now reference the file with an HTML link by using a calculation on a NOTE field:
concat('<a href="file:https://esriza.maps.arcgis.com/sharing/rest/content/items/58bf71eb534741429c03a0f052e0f7fa/data" class="link external button button-raised button-fill color-blue">Open PDF</a>')
I attached the XLSX file for your reference to this post...
I hope this helps!