Tagging files based on multiple rules?

I have a folder which collects PDFs prior to me getting round to sorting them. I've created a bunch of rules to look for certain content words and apply relevant tags as an interim filing solution. The problem I have hit is that the multiple rules could be relevant for a file but the ordering means only the first one is executed. Is there a way for all rules to be processed against a file, not just the first one to match?
The following is an example of whats causing the problem.
If contents contain DVLA then tag DVLA, CAR
if contents contain BMW then tag CAR, BMW
if contents contain Volvo then tag CAR, VOLVO
The document which first tripped things up was a letter from the DVLA about the BMW, which I'm my original plan should have been tagged DVLA, CAR, BMW but as you can imagine it only gets tagged as DVLA, CAR as that is the first rule that triggers.
As it stands I have around 15 tagging rules created of which a good number are co-dependent. Can anyone suggest a way forward or around the problem?
Dave
The following is an example of whats causing the problem.
If contents contain DVLA then tag DVLA, CAR
if contents contain BMW then tag CAR, BMW
if contents contain Volvo then tag CAR, VOLVO
The document which first tripped things up was a letter from the DVLA about the BMW, which I'm my original plan should have been tagged DVLA, CAR, BMW but as you can imagine it only gets tagged as DVLA, CAR as that is the first rule that triggers.
As it stands I have around 15 tagging rules created of which a good number are co-dependent. Can anyone suggest a way forward or around the problem?
Dave