Mass Fax Use Case with Dataloader:
I would like to attach an existing PDF document to multiple records at once that will trigger the A5 Fax automation rule. How can I do this without needing to write an APEX trigger or use another document generating app?

Consulting Reply:
You can do this through using Data-loader feature in your Salesforce. See this article for more information and steps for how to configure mass upload of PDF attachment to multiple records at once:

DATA-LOADER . CSV FILE: In summary, Data-loader will allow you to get all your records from preferred object into a .csv file and then use the file path for the one existing PDF attachment that you are wanting to fax. Then Data-loader attaches the same document to every record on the .csv file (attaching to multiple records in Salesforce). Uploading an attachment to multiple records will copy it on each record.

-FAX AUTOMATION: Then configure an A5 Fax automation rule that should fire the fax to be sent once the document is attached to record.

-ATTACHMENT TYPE: You need to make sure that you are uploaded the PDF as an Attachment TYPE and not File type (our automation feature will only working with Notes & Attachments related list with PDF type attachment and will not work with Files type under Files related list).

-MASS DELETE ATTACHMENT: You can mass delete the attachments afterwards using instructions found here.

-MASS FAX OPTIONS: This is just one way to setup a mass faxing process. You can also use a document generation app with output format PDF to setup a mass attachment to multiple records at once, our A5 Documents is one option or Conga. A5 Fax is a pretty straightforward app that sends the attachments on a record to the number provided (ex. in an object field on that record or in attachment filename). So you need a PDF attachment on any record that you want to send to.