You can use snapshot labels to determine what version of a document is translated.
You may want to apply a snapshot label to a project before starting a translation job.
When source-language documents are packaged for translation using a snapshot label, that same label is added to the root element of each document when these documents are imported into the target-language cabinet. For example, if the Start Translation dialog specifies the Filtering option as Snapshot Label, and the Snapshot Label value is 1.0, then a snapshot of 1.0 is set on the target document when it is imported, with a date matching the date of import. This enables users to process (through Publish, Export or Create Edition) the labeled version of a target language document, matching the labeled version of the corresponding source language document. Snapshot labels can also be used to control how existing translations are handled when using Release Management. See How Release Management Handles Existing Translated Content.