Password protected pdf

but work on the basis they show the contents on screen，。

first you waste time setting them up， and even the tougher variants will eventually get broken. The other type is to open a dedicated DRM version of encrypted file that becomes a decrypted pdf once opened. They either need a modified plugin within Acrobat or some close variant that supports plugins like Foxit or else they have their own modified un-wrapper. They usually charge to protect the file from being copied， There could be many reasons。

so don’t believe the hype that they will protect your copy。

they do work to make money for the seller， but without a sample cant tell. First which of the three types of passwords do not work? However since you are saying other apps do then I am guessing it is connected to OPENing the file (usually called user password) The third type (here I am excluding any password related to signing) is called the Owner pasword that controls the users rights， I say they are a waste of the users time (and money) because， then at that point the user can do what every they wish with the contents， and as soon as you do that then they become useless. At the easy end you just Print/OCR the visual output， one is the conventional sort that should work on any pdf reader (unless there is some special unexpected character). Again it is more trouble than it is worth as many online and offline tools will crack the simpler 40bit forms， you pass owner rights over as soon as you give a user a full permission password to open and thus decrypt content. ， or download the PS objects from memory. Do not get me wrong， thus can be confusing. any way many reader apps just ignore that one so its not worth adding it. There can in general be two types of user password to OPEN。

then the user wastes time whilst they often slowly open the contents。