If you have access the repository itself (not a working copy), you should be able to dump the current repository, filter it to only include information about the docs folder, and load it into the other repository.
Would be something like this:
svnadmin dump /svn/old_repos > ./repository.dump
svndumpfilter include path/to/docs --drop-empty-revs --renumber-revs --preserve-revprops < ./repository.dump > ./docs_only.dump
svnadmin load /svn/new_repos < ./docs_only.dump
Without access to the repository, you cannot maintain the revision history and you have to settle for copying the files into the new repository and committing.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…