Hello!Thank you for your question. I am Shefin and I look forward to helping you with your issue today.
Please try the following and try scanning again.
Then, click the + (plus sign that you see on the print & scan window, and not on the keyboard) sign to add printer. Select your printer from the list.
Note : Make sure that you are resetting the printing system before adding the printer.
If the issue still persists, try scanning using Image capture. Follow the instructions in the link below.
If the issue persists, or you have any questions, please be back and let me know.If you appreciate my service, please rate it EXCELLENT by clicking the EXCELLENT (5 Stars) and Submit. My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Thank you for your business!Thank you!S H E F I N
Do you have Brother Control center installed in your computer?
May I know the scanning software you were using to scan pdf?
S H E F I N
In your applications, check if you have brother Control center listed. You cannot scan pdf with Apple preview. You need a different software like Adobe Acrobat Pro.
Please go to the link below, download and install the scanner driver, which includes control center.
After installing that, open Control center and try scan to pdf.