If inserting images of PDF pages, compress them first so the .tns file doesn't become too laggy on the handheld.

For older models, this legacy software allows for basic file transfers.

Save the file as a .tns and use a USB cable to sync it to your handheld via the "Content Explorer" tab. Why "Full" Free Online Converters Are Rare

You can open the software, create a new TNS document, and manually copy-paste text or insert images from your PDF.

Because of these structural differences, a direct "one-click" converter that transforms a PDF into a fully interactive TNS file does not exist. However, you can use specific software to transfer PDF content into the TI-Nspire environment. Best Tools for TI-Nspire File Management

Insert those images into a TNS document using the Student Software. This preserves the exact layout of the original PDF. How to Manually Convert PDF Content to TNS

This is the standard desktop application for managing CX and CX II calculators.