Zotero

To include a PDF or any other file from your computer in Zotero, simply drag it to Zotero — you can drag to an existing item to attach the file or drag between items to store as an independent item.

You can also add add files as attachments to existing Zotero items by right-clicking on the Zotero item and choosing “Add Attachment” or clicking the paperclip icon in the Zotero toolbar. You can also add independent file items by clicking the green plus sign  in the Zotero toolbar and choosing “Store Copy of File…” or “Link to File…”.

For PDFs that you have added as independent items, you can try to automatically download bibliographic data from the internet by right-clicking them and selecting Retrieve Metadata for PDF. Note that this function will typically yield lower quality metadata than importing using a Web translator.