Unfortunately, no. File references don't work that way, whether they're SW references are created via Paste As Reference. The only value to the references is that you can see them in the Contains tab and you can move them all together through workflow transitions, if the system is setup correctly.
What you could do is to add a card variable for component PDFs (500XXX series in your case) and enter the number of the containing PDF (2900XXX series in your case). That done, you can search for files where the new variable contains the 2900XXX in question and the result will show in a file list pane, rather than in the Contains tab pane. There you can mass select and paste to your heart's content.
The PITA is to manually enter the 2900 number into the variable for each 500 PDF, but that could possibly be automated through Dispatch, etc.
I was able to go into the contains tab, click on the 2900XXX file and do a copy tree.
I put it in a folder that I created on my desk top (on the fly) and it takes a copy of all the referenced files.
Then I can quickly open up the folder and move all the files to my email in one swoop. Works nice.
takes about 30 seconds versus the 20 minutes of pecking through a bom. I just have to maintain the pasted references in the future for an EC's that come through,