Apply a restriction to allow opening only in Acrobat Reader

I don't know, I'm an Acrobat expert, not a Firefox one.

But you should use only this line:

this.getField("cache").display = display.hidden;

If it doesn't work, the rest won't work either, especially the conditions.

I re-tested these two documents today, both works fine with Acrobat, with Foxit Reader and with MS Edge.

With Qoppa PDF Studio only the layer tip works, not the hidden field.

I can't test with Chrome because I don't want to install this spyware on my computer.

"I have generated a PDF file, which includes a pop-up awareness message recommending the use of Acrobat Reader to fill out the form. However, users continue to ignore this message and fill out the form via web browsers and other applications such as Sumatra, Foxit, Nitro, and others."

This makes complete sense: software that doesn't support AcroForms and/or JavaScript can't display your alert, so users won't see it.

This is a document I made.

Copy-paste this URL in Google Translate, you will find all the explanations here:

https://www.abracadabrapdf.net/ressources-et-tutos/js-et-formulaires-ressources/forcer-utilisation-pdf-avec-un-vrai-pdf-reader/

See as well:

https://www.abracadabrapdf.net/ressources-et-tutos/js-et-formulaires-ressources/forcer-utilisation-pdf-avec-acrobat/

@JR Boulay