Printing Multiple Invoices at Once
Create a url like http://mysite.com/arinvoiceviewfpdf.php?invoiceidstr=146,147,148,149,150
You can get the invoice ID for an invoice by going to Reports -> Summary of Invoices.
In the first column hover over the invoice number. Look in the status bar at the bottom of the web browser. The invoiceid is in the URL string.
You can add many more invoice IDs to the url string, but there may be a limit to the length of a url that will fit in an address bar (maybe 100 or 200 IDs for example).