How to Update an exsiting File in an Assignment

Summary

I'm wanting to add a file to an assignment but if changes are required to the document that I can just edit the file and re-save this without adding a new Assignment to a Learning

Content

I have a word document attached to an assignment and have mapped this to a Learning Plan. Each person needs to complete the attached word document and then re-load this back into the assignment which then will be reviewed and marked completed.  However if this document is required to be changed in 18mths can I update this and re-save the document without re-moving it from the existing assignment which is mapped to the Learning Plan. If I have to remove the old Assignment from the Learning Plan and add the new Assignment that has the updated version then will make the Users