How to add attachments to products in PrestaShop 1.5-1.6
In the admin panel of PrestaShop there are options with which you can add product attachments which can then be downloaded from the frontend by any visitor. If a product has files attached to it, they are listed on its page on the frontend and can be downloaded from there. You can attach whatever type of file you want (e.g. text files, PDF, images, etc.).
Upload Attachment Files and Associate them with Products
To add an attachment to a product, go to Catalog menu>Products sub-menu and edit the product. On the form for adding/editing the product click on the Attachments tab on the left. On the page that opens type a name for the attachment in the Filename field and optionally a short description in the Description field. Then click on the Add file button (in PrestaShop 1.5 it's Browse) and select the file from your local computer. The file will be uploaded automatically; in PrestaShop 1.5, however, you have to click on the button Upload attachment file that's under the options.
Below the options for adding an attachment there are a couple of text fields: Available attachments and Attachments for this product. In order for an attachment to be shown on the product's page on the frontend it has to be listed in Attachments for this product. To move an attachment from one text area to the other, mark it and click on the Add or Remove button (depending on where it's listed). After you're ready with all the options click on the Save and stay or on the Save button.
Edit and Delete Product Attachments
To delete any of the product attachments or to edit the name and/or description options of any of the uploaded attachments, go to Catalog menu>Attachments sub-menu. On the page that opens there's a table that lists all attachments. To edit or delete an attachment click on the respective button in the table. From this section of the admin panel you can also upload new attachments but you can't add them to products. You have to do this from the settings of the particular product.
For screenshots and some more details you can read the tutorial on how to add and manage product attachments in PrestaShop.