Hi Dib,
Thank you for using Syncfusion products.
Yes, it is possible to zoom the loaded Pdfdocument in PdfViewer control from codebehind and using document toolbar. But at present we do not have support for mouse zooming through mouse weel.
Could you please report this issue through Direct Trac Developer Support System (https://www.syncfusion.com/account/login?ReturnUrl=%2fsupport%2fdirecttrac%2fincidents because you can take the advantage of the expertise of a dedicated support engineer and a guaranteed response time and we hope you will take advantage of this system as well. If you have already reported, please ignore this.
Please let us know if you have any other questions.
Regards,
Meikandan