If you sign up for our $18 plan, you will be allowed to use remotely hosted files. So you will basically upload your files to your website. Then while adding a product to E-junkie, press "more options" and specify the URL of the file in the remote url field.
As for using frontpage, please find the option which will let you paste HTML in frontpage and then just copy the button code E-junkie provides you and paste it in your webpage.