Form 8283 Section B # {PrefixNum} : For electronic filing purposes, an appraiser signature document must be included as a binary attachment.

basically the appraiser signature needs to be uploaded  as a pdf  

you can do so on Screen 4.4 misc /pdf

1. Go to Screen 4, Electronic Filing.
2. Click on the PDF Attachment button.
3. Click on the Attach PDF button.
4. Select Browse Files.
5. Choose the PDF you need to attach.
6. Click on Open.
7. Press on OK.
8. Select the form/type to link the attachment to from the Link to form Form 8283
   • If the attachment is only for the state return, set the Send PDF attachment with federal return radio button to "No".
9. If your state allows PDF attachments, a separate section will be displayed for state information at the bottom of this screen. Check the Send PDF attachment with [state] return box, if applicable.
10. Complete any state information that applies. These fields will vary by state