First and foremost, as with any lettered updates, your DM and/or SM must already be running the same major version of TechDoc to perform the upgrade. In other words, to apply TechDoc 7b, your server must already be running TechDoc 7, 7a, or 7b to proceed. And yes, you can always safely reapply an update against itself. As always, each SM should be updated before any DM(s) that populates it. DM's do not need to be immediately updated (you could wait weeks or months); they just need to be updated last.
If you wish to access TechDoc download files, you are required to create an account on DocuBrain. The process is easy. Simply go to https://docubrain.com/ and click on "Create new account" in the upper right corner. On the user account screen, you must enter a username and your e-mail address. In order to avoid spam bots, we currently approve each account before it can be accessed. You will receive mail that will lead you through the remainder of the process to enter your password.
After your account has been activated, you can use the menu Products>TechDoc>Downloads>Release 7 to navigate to the download. You have to download both files. You run TechDocJava7bSetup.exe first, and TechDoc7bPatch.exe second. As part of this patch, it has to update the SQL database so you need to know a SQL dbo account password on the DM and/or SM database(s) to perform the patch.
A reboot is not required. However, the Tomcat service is shutdown as part of the upgrade. So there is definitely a service interruption to users.