What are various printing option in Book Keeper | Printer Option | Printer 

If you want to print with Book Keeper Windows, you can use any printer (Laser, Inkjet, Dot Matrix)
Just attach printer, install drivers and take print from Microsoft Word.
If it works in Microsoft Word, it will work in Book Keeper Windows.
Video Tutorial (A4, A5 Printing): https://www.youtube.com/watch?v=jFETXc_FmOY
Video Tutorial (Thermal Printing): https://www.youtube.com/watch?v=E4-MQGHx_O0

For Book Keeper Android, (Thermal Printers), we’ll recommend,
Epson TM-P20
Cashino Printers
NGX Printers
ESY POS
Video Tutorial (Thermal Printing): https://www.youtube.com/watch?v=3rN7Fy9QxGw

For Book Keeper Android (Wireless Printers),
check below link: https://www.google.com/cloudprint/learn/printers/

For Book Keeper iOS, you can print with any printer that is compatible with Air Print.
Learn More for Air Print: https://support.apple.com/en-us/HT201387

Some sample Printers Links:
HP Deskjet 2331: https://amzn.to/34n949X

HP InkTank WIFI Printer: https://amzn.to/3fqt3dY (works with Android, iOS and Windows)

A4 Sheet for printout: https://amzn.to/3uAtnLO

Epson TM P20 Bluetooth Printer: https://amzn.to/2QZXrCB

TVS Barcode Scanner: https://www.amazon.in/TVSE-101-Ultrascan-Decoding-Technology/dp/B00HWOU0IO/