How can I set data validation on Upload button?

To be specific, i would like my clients to name the document in a way i request them to do so before uploading. e.g. the document name <has to contain 'application form'> something like this. Otherwise jotform can reject the uploading. How can i do that?

Unfortunately, this isn't possible in the form builder. However, you can add a description or a text on your form telling the users that they need to name their file according to your preferences.

Another workaround for this is to download the full source code of your form and implement a Javascript validation to check the file name before uploading the file. Here's the guide on How to get the Full Source Code of your Form.

Hope this helps. Let us know if you need further assistance.