Usually a software product will have both pre-sales documents and post-sales documents.
The pre-sales documents are used “before sales”, so the primary intention of pre-sales documents is to trigger the customer’s interests, so usually pre-sales documents are brief, succinct, attractive, fascinating, and/or tailored for the certain customer, industry or solution needs. The target readers of pre-sales documents are somewhat decision makers or shapers, but not necessarily the end users. For example, fancy and brief slides, an executive summary, or a nice brochure is a pre-sales document.
On the other side, the post-sales documents are used “after sales”; the target readers are most probably the end users, so usually the post-sales documents are supposed to help the end user to understand deeply about the product, how it works, and trouble shooting. So usually post-sales documents are much detailed and technical. A product function explaining (specification, anatomy or some other words), or a detailed user manual is a good example of post-sales document.
Recently I met a problem when I was doing work to release a new version of my product (a big enterprise software) to the market. I found some documents were used as pre-sales documents as well as post-sales documents. We had much controversy, debates and arguments when we were reviewing such “dual purpose” documents. For the same paragraph, some marketing colleagues thought the words were OK since they were from a marketing/pre-sales point of view; however some other colleagues did not like the words since they were from a post-sales point of view.
I believed the root reason of the controversy was the confusion by the “dual purpose”. After all, there are distinctive differences between pre-sales and post-sales documents, so I think we just should not place a same document as both pre-sales and post-sales document. I think it just does not work well. We should be aware of the distinctive different purpose, target readers of the two kinds of documents. We should not give a certain document “dual identity“. It should be for pre-sales, or it should be for post-sales. But never both.