Control center for some Brother printers, which you launch from the system tray, has items to select the type of scan. It may show type "File" for scanning to PDF.
Some newer Brothers no longer include that. The iPrint and Scan utility replaced it and can be downloaded an installed from Brother at
https://support.brother.com/g/b/productsearch.aspx?c=us&lang=en&content=dl
Additionally, Paper Port is available to install for some models.
All of these have options to select the type of can (JPG, PDF, etc.)
The Windows Scan utility mentioned in the AI answer is also an option and is available for free here -
https://apps.microsoft.com/detail/9wzdncrfj3pv?hl=en-US&gl=US