How to rename Quote-PDF

Whenever I export an Quote / Estimate, the Name of the QUote is like this:
"Quotes_1370079554403.pdf"

I dont want to use the zohogenerated quotes-number. Too long...
So i delete this and replaced with an new custum autonumber field.

Now my Quotes have a number like "A-12344". Perfect!
BUT - when exporting, the zohogenerated Number is shown in PDF-Name:
"Quotes_1370079554403"... How to change? Or is this really! not possible?

I want to use the Name of the Quote like: A-12344. Or - much better- "Custumername_Angebot_A12344.pdf"

best regards from Vienna
Marco