Chrome //
Extensions 
Chrome
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Transfer Dropbox to Google Drive
Directly transfer files from Dropbox to Google Drive and vice versa. No download and re-upload.
YouTube Uploader for Dropbox, Drive
This app allows you to upload Dropbox, MS OneDrive, Google Drive video files to YouTube directly.
Drive Files to Dropbox™
This app is a file transfer, backup tool for Google Drive. It allow you to save Google Drive's files to Dropbox™ folder directly.
PDF Editor for Drive, Dropbox
Edit PDF files for free for Google Drive, Dropbox. You can add annotate, text, images, form field, freehand, highlight, and more.
File Converter for Drive, Dropbox
Provide a free, simple file converter. Convert any document, archive, spreadsheet, audio and video file from one format to another.