Hello,
Try this:
Connect to SAP Software Download Center
Select Support Packages and Patches > A-Z Index > P > SYBASE POWERDESIGNER > SYBASE POWERDESIGNER 16.5.
In Support Packages and Patches - P, click SYBASE POWERDESIGNER 16.5. Do not select SYBASE POWERDESIGNER SE 16.5.
Click SYBASE PD VIEWER 16.5.
Click a platform to download the corresponding product.
HTH