I've never seen this before, and I've been using the Preview method described above for 15+ years. I have also never installed an Adobe product on a mac, ever. Do you have a link to a file that can produce this error in Mac Preview? It would be fun to learn how to bypass that.
It does get by the "Please wait..." that you get in Preview or Chrome but Firefox 93.0 doesn't actually load the form properly (e.g. it's 6 pages in Acrobat but only 3 pages in Firefox and those 3 pages aren't even rendered properly).
Which version? For me 90.0 shows the "Please wait" message which some JavaScript or something is supposed to replace, and 93.0 force downloads it, even when I try to open it from a local file.
All / most PDF forms used by the Australian Defence Force are like this - I suspect it’s because it’s all tied into the identity / ability to digitally sign the forms.
It’s very frustrating when you send someone (externally) a PDF and it required them to install Acrobat.
Or maybe it’s just Adobe trying to take the P out of PDF…
They may not be accepted by the form issuer if they have a process to pull the text out of specific fields in the PDF. I have run into that before. They are not just looking at the document but processing it.
You might try filing you FBAR, which if you get wrong results in criminal penalties, and which (practically) every American living overseas needs to complete each year:
My employer uses a training and document system (third party) that requires the use of Acrobat to view PDFs. I never have to fill out forms within the PDFs; I simply can't open the files via Preview (or Firefox). Apparently the provider inserts JavaScript into the published documents (which, I assume, track document usage, since it is a training system).
Also, I can't post a link to the document, since it contains proprietary training materials.