Audience
The intended audience for the help docs is primarily users of the SaaS product. The language used should be easy to understand and avoid using technical jargon, unless you know that the user will have a good level of understanding. Remember, sometimes it's easier to understand the "jargon" in a field, than to understand a more "simple" way of writing things.
Tone
The tone of the help docs should be friendly and helpful. Use a conversational tone to make the information easy to understand and approachable. Imagine that you are looking over the user's shoulder and giving them helpful advice.
Format
Use headings and subheadings to break up the text and make it easy for users to find the information they need. Use bullet points and numbered lists to organize information. Use screenshots and videos to illustrate how to use the product. Technical Writing One is a useful course from Google.
Voice
Use the second person voice (you, your) to address the user directly.
Grammar
Use proper grammar and punctuation. Avoid using slang or colloquial language. This is especially true when your users may not be native speakers of your language. While it's true that people learn "it's raining cats and dogs", they might not understand "a cat in hell's chance"!
Capitalization
Use sentence case for headings and subheadings. It's much easier to scan and understand. Capitalize UI (user interface) words, such as "Print button" and "Save".
Branding
Use the SaaS product's branding, such as the logo and color scheme, throughout the help docs. Keep the docs on the same domain as the marketing pages for better SEO. If you must use a sub-domain, always link to the webpages and the app from the docs.
Linking
Use hyperlinks to link to relevant information and resources within the help docs and on the SaaS website. This helps people find additional information, and will help convert visitors into users.
Feedback
Encourage users to provide feedback on the help docs and use that feedback to continually improve the documentation over time. Hyvor Talk creates a comments section at the bottom of your docs.
Update
Keep the help docs up-to-date with any new features or changes to the product.
In conclusion, the help docs should be easy to understand, approachable, and helpful. Using a consistent format, simple language, and a friendly tone, users can easily find the information they need to get the most out of the SaaS product. It is important to keep the help docs up-to-date and encourage user feedback to continually improve the documentation over time.