Linking specs to project stages/ to do items

It would be useful to be able to add specs (or files) to a To Do item or project stage.

When undertaking a task it is useful to know what tools/ files/ specifications are needed for a task (e.g. having a similar check box to the one used to indicate which employees are involved).
This would allow you to plan the ordering of supplies based on the project timing.

It feels at present as though the specs sit out on their own yet they need to be linked to the tasks and to the billing.