If you wants to add your company logo on your invoice,so you can follow given steps:
Step 1:Go to Administration menu,
Step 2:Click Configuration,
Step 3:Click Invoice/Document Prinitng,
Step 4:Click on standard,Select sales,
Step 5:Here you can see the option is Print Logo,Specify Y,
Step 6:Please provide the path to the location where your logo has been placed on your system,make sure you logo image should be jpeg format,
Step 7:Set Position as top left,then mention height and width,save this window.
Now you can go to the transaction menu,click on sales and open any invoice in modify mode,give print command,you logo will be shown on your printout.