Hi, I have 17 word files with 400 to 700 pages in each file. Please advise on how to merge all the files in to one file and remove duplicates

You would have to copy and paste into one document

Each file would be of 400 to 500 pages and how can I consolidate into one file and ms word becomes slow and does not work properly if the file size increases.

The fact is that the only way to combine several files into one is copy and paste. That's what you asked to do. And that's what I answered. If that solution doesn't work for you, then you need to look at an alternative. In that case, you need to explain what these files are and what you are trying to do with them. Only then can we offer alternatives.