I managed to scan my expenses receipts and attached them to expenses linked to a customer and to to project while on the road.

great Zoho Books

then at the end of each week, i need to send to the customer one invoice with all the expenses of the week. 

great again Zoho  Books with all the 15 or so expenses linked to one expense invoice.

But then my customers ask for a copy (pdf) of each expenses receipt... I do have them in Zoho books but i can only link 5 of them to an invoice.

How do i do that  for 15 receipts ?