Rich is correct above, but with some variations and issues. In some browsers, after finding and choosing "Save as", you have 3 choices, and "Web Page Complete" seems to provide the best option. However, you are still only saving a true copy of a webpage to your hard drive. That means that anything on that page (photos, diagrams or web links) that works as a "link" will only be there as long as the linked material is still available. Remember the thread issues we've had before when various photo servers closed down?
And, true, you can save an entire page as a PDF file, but then you have all the usual PDF file issues. For example, some individual posts will be "split" across multiple PDF pages, and the user will be unable to copy and paste anything (text or photos) from the PDF file, unless you acquire the very expensive Acrobat program. Unlike Rich's method, though, the PDF process does give you permanent copies of photos, diagrams and web links.
I can't comment on the MS Word 2015 method of saving forum posts because I don't have it, but I would suggest that if you use that method, check to see what is really saved on your hard drive. Be sure that you have actual photos and diagrams in your file and not just links back to the OGR forum page or some other web location. How to check? Put your cursor over the photo or diagram and wait a few seconds; if a web-link box pops up, you will know that's what you have and that it might be lost some time in the future.