PDFUnlock! Blog

I don't know the password - that's why I came to you!

Wed, 07 Sep 2011 04:17:42 -0400

The two different types of passwords used in PDF files are, and will always be, a source of confusion.

The OWNER PASSWORD is used to control what you can do with/to the PDF file, but you do not have to know it in order to open and view the file. If the owner password is in play, looking at the document’s security properties will tell you what you can’t do. With the right software or a website such has www.pdfunlock.com, the owner password can be removed instantly.

The USER PASSWORD on the other hand, is only used to prevent anyone who doesn’t know it from opening and viewing the file.

A user password, if not known, cannot be removed instantly. This is why we ask you to provide it if you upload a PDF file protected with one to www.pdfunlock.com. If it is known, we can remove it from the file and free you from the inconvenience of having to remember it and provide it every time you open the file.

If the password is not known, our options to help you are very limited. First, the strength and type of the encryption needs to be evaluated. Passwords of the oldest type, also known as RC4 40bit, can always be removed. This is an operation that requires lots of computing power, but is always within reasonable limits. Since last month, we offer a fully automated service that guarantees the removal of such passwords in less than an hour. However, due to the cost we incur by launching tens of high-end servers to unlock the file in such a short period of time, this service comes cannot be offered for free. To purchase this service, just upload the file at www.pdfunlock.com, and you will be presented with instructions how to proceed. The other option would be to purchase the appropriate software, such as GuaPDF, and run it on your computer. Expect it take anything from a few hours to couple of days, depending on your computer. It will also consume all the CPU power available, making using the computer for anything else hard.

Removing user passwords that utilize newer encryption, such as 128bit RC4 or AES (128bit or 256bit) is different. It’s fair to say that there are no guarantees that, with currently modern computers, such a password would ever be removed. There are simply too many possibilities. The key here becomes knowing something about the password, and using that knowledge to somehow limit the passwords that are attempted. Any experiences with removing this type of passwords would be appreciated in the comments!

What do you mean it's "not valid"?

Wed, 24 Aug 2011 00:57:00 -0400

Two other error messages we show many of you say:

The uploaded file does not seem to be a valid PDF file

and

The uploaded file seems to contain errors and cannot be unlocked

What these really mean is that the underlying software encountered something unexpected while processing your file.

Well-formed PDF files conform to the PDF specification. Malformed PDF files, for whatever reason, do not. For example, some PDF programs may deliberately generate PDF files that are malformed; they can deviate from the specification to add nifty features to the files that only their program supports. Other PDF programs have bugs and inadvertently fail to fully conform to the specification.

In addition, PDF readers vary in how they deal with PDF files that do not follow the PDF specification 100%. Some may simply ignore it, while others actually try to fix the errors for you. Either way, there is a good chance that what really is a malformed PDF file opens just fine in some PDF readers.

When you encounter these error messages, you may want to double check that the file you uploaded can be opened in a PDF reader. If not, your copy is evidently corrupt and you should, if possible, try to get a new copy.

If it opens fine, there is unfortunately nothing we can do in the short term to fix it for you. In the longer term, hopefully the PDF software industry as a whole will keep working on improving its adherence to the specification. Only this will keep PDF (Portable Document Format) files truly portable.

What do you mean it's "not secured"?

Sun, 21 Aug 2011 03:46:00 -0400

All the error messages that people see are logged for later analytics.

Something that puzzles us is that on a normal day, the following error message is shown more than a thousand times:

The uploaded file is not secured and does not have any restrictions that can be removed

This happens when a PDF file that has no security restrictions applied to it is uploaded. The picture above shows how the security properties of these look like in a PDF reader (look for Properties under the File menu).

Have you seen this? Would you please leave a comment here and help us understand what it is you can’t do with your PDF file?

Secure Connection Now Available

Wed, 20 Apr 2011 00:16:22 -0400

Before sending files across the Internet, one should always consider the security of doing so, the worst case scenario being that an unintended and ill-willing party gets a hold of the file.

If the files are already available to the public, there is no risk in sending them. If they contain personal or otherwise confidential information, think twice.

We take your privacy seriously, and our server is secured by the industry standard practices. The uploaded and unlocked files are not made available to anyone except the uploader herself.

Last week we added another security related measure by enabling secure (https) connections for those who wish to make sure that the data sent back and forth between their browser and our server is encrypted and virtually impossible for a third party to decipher.

To enable the secure connection, point your browser to https://www.pdfunlock.com

Happy unlocking!

Liked by a Thousand

Wed, 29 Sep 2010 18:50:25 -0400

We just want to say thanks to all of you who have shown your appreciation of the service by “liking” this page on Facebook - it helps us keep this free!

Many of you have reached out to us and asked about privacy. The files you upload are not made available for anyone. The unlocked file is only made available for the uploader of the original file. Both files are temporarily stored on our server, but get removed by an automated process which runs on short intervals. All this said - keep in mind that sending information over the internet is always coupled with a risk. We have done, and do, our best to keep our end secure.

How did PDFUnlock! save your day?

Sun, 02 Aug 2009 11:57:40 -0400

Had trouble with a restricted PDF file? Couldn’t copy and paste, couldn’t print the way you wanted, fill forms etc? If you got helped by PDFUnlock! and want to share your story - please leave a comment!