It has been one of the “little secrets” of Acrobat since version 4, that loading a fillable form under the browser can take quite a long time, or that all of a sudden the form does not react for some time.
It has been one of the “little secrets” of Acrobat since version 4, that loading a fillable form under the browser can take quite a long time, or that all of a sudden the form does not react for some time.