If you have questions about Pix4D outputs, we wanted to remind that Pix4D outputs are compatible with many 3rd party software. You can send the needed output files to your clients via email, Dropbox, WeTransfer, etc.. They don't need to use Pix4D software to open them.
The processing results can be found in the project folder. For more information about the project folder structure: https://support.pix4d.com/hc/en-us/articles/202558649.
For more information about Pix4D outputs in third party software: https://support.pix4d.com/hc/en-us/articles/202558499
If you process your project on Pix4D Cloud, you can share the results with the Share button and your clients will be able to visualize the project on their browser: https://support.pix4d.com/hc/en-us/articles/215858503-FAQ-Pix4D-Cloud-General#label12