I have one similar problem. I've been toying on a couple of ideas. If I manage to do it, I will share.

That said, AF can be really akward in certain moments....

Ok, done with CSV instead of PDF but I guess the principles will apply.

A bit convoluted, but couldn't find other way:

Notice I have 2 aggregations, one per each CSV I will attach.

I need to put the in sequence (and yes, that means that if you want attach 3, then you need to create another aggregation group)

IMPORTANT trick: control the number of OUTPUT bundles of each component. For example, the two queries before each aggregation are to count the number of elements I will get in each CSV.... in one execution I forgot to apply the filters... and I ended with 171 mails in my inbox... as the aggregation will be executed once PER each output bundle of the previous component

HTH

(P.S. If anybody find another way to do it, simplier... please share)

Thank You Guillermo. Will check with this solution