Firstly, you will need to add tags to the contractors that are only 'Maintenance' - Tags will be used in mail merge to select a specific group you wish to send too.
Secondly, create email mail merge:. https://propertytree.elevio.help/en/articles/92749
Add the Bricks + Agent trade PDF attachment within the email as a 'link to attachment' : https://propertytree.elevio.help/en/articles/93088-add-attachment-to-email-template
Processing bulk email mail merge:
Selecting the correct filters:
Also select the correct TAG group
This will avoid sending out the email to all of your Property Tree creditors IE Water, Starata, etc