Using the "USE PROPERTY FILE" feature
This seems pretty obvious, but I can't seem to find where / how to add these property files.
This modal pop out is accessible via the WYSIWYG editor after clicking the paperclip attachment icon.
@Kirk-Nankivell Happy to help with this as it can be a little tricky if you're not sure where to go.
So, first you'll go to Setup > Custom Fields > Property and create a custom field where the Data Type is a file upload. Note: You can either upload a default file or leave it blank - leave blank if different properties will require different files. Then, you'll go to the property where you want to apply the custom file (Properties > Properties > [Property name] > Custom Fields) and, using the "More Actions" (three lines) drop-down to the right of the custom field, upload or replace (Delete and Upload) the file. Once you've selected the file for that property's custom field, it will be accessible to attach in your inquiry correspondence, as shown above.
I hope this helps!
@amber-d thank you so much! Yes it is a bit hidden.
On the previous screenshot, it might be worth including a link to "Add a new property file?" or something like.
Agreed! Thank you for the feedback!