Zotfile is a Zotero plugin to manage your attachments: automatically rename, move, and attach PDFs (or other files) to Zotero items, sync PDFs from your Zotero library to your (mobile) PDF reader (e.g. an iPad, Android tablet, etc.) and extract annotations from PDF files.
You might want to use ZotFile if you have ever hit the limit on the free Zotero storage. You can use ZotFile to easily rename and move PDFs; combine it with UVA's Box for unlimited cloud storage.
You can merge records in order to remove duplicate records in Zotero. Select Duplicate Items on the left, and Zotero will display all the records it thinks are duplicates. Select the Merge button on the right.
If the versions are slightly different, Zotero will display the differences, and you can select a master item.