1. From OPEN FILE tab, click View & Edit.
2. Open a file from your Google Drive or Dropbox.
You can also choose to open a file while viewing a document, from the top navigation bar.
3. Once you're finished annotating the document, click Save. If the original document is stored in Google Drive, choose to save to Google Drive, and if the original document is stored in Dropbox, save to Dropbox. The annotated document is now available in Google Drive or Dropbox.
Saving back to Google Drive and Dropbox is not available for merging PDFs or organizing pages. In these cases, saving a document to Google Drive or Dropbox will create a new document.