Hi,
If you don't want to store the printed reports, try unticking "Reload from Attachment?" and "Save as Attachment Prefix" empty in the reports menu.

* Enable debug mode
* Navigate to Reports menu under settings -> technical

* search and open report and apply the change for above mentioned fields

Thanks

i have written a cronjob to delete the invoice pdfs in the filestore.

1.use query SELECT store_fname FROM ir_attachment WHERE res_model= 'account.move' to get the location of the invoice pdf

2.delete the file from the file store.

3. use DELETE FROM ir_attachment WHERE res_model= 'account.move' to delete the record in ir_attachment table