How do you prevent PDFs created from Excel files in Flexcel from being edited?
I basically want to make them read-only, ie no pasting into them and no editing allowed.
Thanks.
Well, this was answered by email, but I'll paste the answer here for if anyone else is interested:
Hi,
Currently FlexCel doesn't support protecting pdfs, basically because the "protection" is a big lie. When you protect a pdf the file just gets a record that says "this pdf is protected", and if you open it in acrobat reader acrobat will refuse to edit it/copy it. But if you open it in other reader you will still be able to edit it, and unprotecting the file is just a google for "unprotect pdf" away. There are thousands of free products to unprotect pdf files in a second.
What we do provide and makes more sense, is the ability to sign the pdf (look for the signing pdf demo). It won't make the file "impossible to edit", because that isn't possible, if the user can read the file, then he can modify it (either by legal ways like printing the file to a new pdf file and editing the new one, or by using an unlocker app). But as it has a digital signature, the modified file will be marked as a forgery by any pdf reader. He might sign the file himself, but he can't resign it with your signature.
I think signatures are the only real way to protect a document. If the bad guy modifies your file, the sign will be broken, and acrobat will put a big red warning. He might even manually retype your full pdf, but he won't be able to sign it in your name. The "protect" function in pdf is just a joke, and it gives a false sense of security, since you think the file can't be modified, and it can very easily.
I would still like the option to protect PDFs, instead of having to obtain a certificate for the signing.
I am aware that the protection is easy to crack, but it's something our users are unlikely to do. I have been asked to provide this type of protection, and I think it should be an additional option. This way we don't have to incur the additional cost of purchasing a certificate.
I just need to show that the PDF is "protected". If it gets broken then so be it. As you said, it's 100% impossible to protect them anyway, but I'm still doing what I've been asked, and at no extra cost.
Hi,
<quote>
I am aware that the protection is easy to crack, but it's something our users are unlikely to do.
</quote>
Users are unlikely to modify pdfs at all. Many people even believe it isn't possible to modify them. A user who knows how to modify a pdf, most likely knows how to crack the protection too. There are even webpages which will unlock them, so you don't even need to install a program in your computer.
<quote>
I have been asked to provide this type of protection, and I think it should be an additional option.
</quote>
As said, I think it is a silly option, but it is hard to fight against the world. I'll see if it can be added, but I can't promise it.
<quote>
This way we don't have to incur the additional cost of purchasing a certificate.
</quote>
If you have any sensitive information that you care that some user might spoof, you should buy a certificate anyway, even if we implement the "protection". Or you might find that someone spoofs your document even when it was "protected", and someone might get in trouble.
<quote>
As you said, it's 100% impossible to protect them anyway, but I'm still doing what I've been asked, and at no extra cost.
</quote>
It is possible to 100% protect them, by signing them. And the problem with the other "protection" isn't that it is not 100% foolproof, it is that it is 0.001% foolproof. I think the only people who can believe this protects anything are managers who don't know any better. But for people trying to break the protection, it is as good as no protection at all. (Actually worse, because the people creating the pdfs might actually think they have some level of "protection".)
About the extra cost, well, it does have an extra cost for us to implement the feature, so it isn't completely without cost. It also adds more lines of code that need to be tested and maintained, for a feature that only seems to be useful to keep the pdf creators thinking they are actually preventing someone to modify something..
But in any case, as said, I will study if it can be done without much development time.
Regards,
Adrian.