Individual files within a Backblaze backup can be directly shared from the View/Restore Files page.
To share a file, an account must first have B2, Backblaze's cloud storage service, enabled via the account settings. Once B2 is enabled, up to 10 GB of data can be stored and shared for free, with up to 1 GB per day of download bandwidth. Additional usage will follow normal Backblaze B2 pricing.
When a file is shared, it will be 'public', accessible by anyone with the direct link to the file.
To share a file, first locate the file within the Backblaze backup via the View/Restore Files page. Once located, select the file name to bring up the dialog shown below. Selecting the 'Share with Link' button will copy the file to B2 under your account, and generate a direct link to the file.
To "unshare" a file and negate the direct link, go to the B2 Cloud Storage "Browse Files" section, and delete the file located inside your b2-share-____ bucket. Click inside the folders to see which files have been shared. From there, select the file you no longer wish to share, and press "delete". That will delete the file from your public bucket and the links to it will no longer work. For a getting started guide for using the Backblaze B2 web interface, refer here.