Yes CCleaner can do that, it's in Tools>Duplicate Finder.
It can't merge different files, but can find duplicates so you can decide if you want to delete them (or not)
It is a lot faster at finding exact duplicates that many others that I have tried.
However it has it's limitations, I use it first to find the exact duplicates, and then use another DF to find the 'almost the sames'.
(Which other DF depends on just what type of files I am looking at, eg for finding <em>similar images</em> I'd use either VisPics or Awesome).
As you are talking about copied/backed-up documents then probably the biggest part what you want to do is find the exact duplicates.
Of course you need to take a bit of care in just what you tell it to look for in order to get the results that you want.
As what you describe should have the same contents then I'd suggest settings like this is a good start.
This will Ignore Sytem files, hidden fies, empty files and Read only files.
In fact I would (and do) keep all those 'Ignores' ticked whenever using it, they are not files that you need to be bothered with normally.
It is set to search C:\Users\steve\Documents for all files that have identical contents.
Note that 'Name' is unticked in the Match by section- because 'document1' and 'document1(copy)' are probably identical contents but have different names so wouldn't be found as identical if you had ticked 'Name'.
<img alt="image.png" class="ipsImage ipsImage_thumbnailed" data-fileid="19319" data-ratio="54.56" data-unique="rdjh3a4xn" width="975" src="<fileStore.core_Attachment>/monthly_2024_08/image.png.d523f29571cc59aed1427ecc1a8d896e.png">
Use the Add button to Browse for the folder and filetypes that you need to scan for.
You can add as many as you want or need and it will compare the files in all of the ticked ones.
You can set it to scan sub-folders, for instance that one above has been set to scan All files in Documents and the sub-folder within Documents:
<img alt="image.png" class="ipsImage ipsImage_thumbnailed" data-fileid="19320" data-ratio="83.90" data-unique="5ndlmu0cm" width="410" src="<fileStore.core_Attachment>/monthly_2024_08/image.png.55fbe490d4798a433a75e8d8f473dc5e.png">
Give it a go like that and see what it finds for you (and how long it takes), you don't have to actually remove them once found
After the Search you will have a list of documents that are exactly identical. There is a button to save that list as a text file.
You then have to decide which ones you want to keep and which not.
(With exact duplicates that's probably going to come down to what Drive/folder each one is in).
One common complaint about CCleaners Duplicate Finder is that you have to tick the files to be removed one-by-one, you can't 'select all'.
That's actually a safety feature, so that you think about what you are doing and don't just delete a load of files by mistake.
Once you have dealt with the exact duplicates then you will still have the modified/edited documents at different versions which are not quite identical.
Whilst you could do things with CCleaners DF to <em>try</em> and find those by searching just on name and not contents, and even using wildcards for the names. I'd suggest that other DF's will do an easier (if slower) job for that by looking for <em>similar</em> content.
(That's why I use other DFs for similar but not identical images, but CCleaner is faster at finding the identical ones so I do those first).