Invoice Customisation Or Picking Slip

[naeaje]

hi does any one know if its possible to add to the invoice pdf

 

1. amount availible - so if theyve ordered 5 and theres only 3 in stock it will say 3

2. previous collected - if they originally had 2 on back order it would say previously collected 3

 

so if i order new stock in and i have a back order once i have updated new stock levels would i be able to somehow refresh the invoice originally made to show now that they have collected the 3 and now 2 are instock - so combining a picking slip with the invoice

 

or can this be done just as picking slip - is there a module for this thanks