The file name of the output file when generating a document package needs to be dynamic (ex: Proposal for Company Name)

You can use our Word/PowerPoint form of the field tag to have values from Salesforce dynamically come in. For example, if you would like the company name and the date to automatically populate, you can use the field tag like the below:

Output Filename: Proposal for <<Account_Name>> - <<Today>>

Any special characters in the file names will be removed when the document is generated. If you use the date tag such as <<Today__a>> (mm/dd/yyyy), the "/" will be removed. (ex: the output will come out as "Proposal for Company Name 112017" instead of "Proposal for Company Name 1/1/2017")

https://help.nintex.com/en-US/docgen/docservices/#docgen-sfdc/Services/templates/FieldTagger.htm?Highlight=field tagger