You are able to store a product description in a several languages. When creating a Product record you can enter up to four descriptions in the available description text areas. (Forgive the Google Translate in the screenshot.) 

The desired description can then automatically be pulled through from the Product when that Product is added to a Quote, Sales Order or Invoice.

You can set this at either Sales document level (on the Quote, Sales Order or Invoice) or on the Company record of the Customer.

Setting the Language at Sales Document level

When creating a new Quote, Sales Order or Invoice you will see a Language picklist. This contains the four languages to which your product description boxes relate. 

When you add a product to a Quote, Sales Order or Invoice the correct description will be pulled through from the product based on language you have selected.

Setting the Language at Company level

The Language field also appears on Company records. This allows you to set a default language at Company level. When you create a Quote, Sales Order or Invoice and link a Company record the Language option will automatically be set based on the Language value set on the Company record.

The PDF which is generated from the relevant module will also use the selected language description.