What is PDF? Why PDF?

This short entry gives a brief overview of what PDF is, and the motivation for its creation. In addition, our goal is to to cite other and more comprehensive sources that can provide more information for interested readers.

Much of the information in this article came from the Wikipedia article on PDF files (http://en.wikipedia.org/wiki/ISO_32000-1), but information from multiple other sources has been weaved into the article, along with the author’s own experience.

What is it?

The Portable Document Format (PDF) is an open standard published by Adobe Systems for representing documents in a manner independent of application software, hardware, and operating systems.

A PDF file is simply a file that adheres to this standard and can be opened by any standard PDF file reader. As an example of free PDF readers, Adobe Reader (available at http://get.adobe.com/reader/) and Foxit Reader (available at http://www.foxitsoftware.com/Secure_PDF_Reader/) are among the most commonly used. A more complete list of readers can be found at http://en.wikipedia.org/wiki/List_of_PDF_software#Viewers.

Each PDF file basically contains a full description of a document, including the text, fonts, graphics, and other information needed to display it. The way that this information is structured is specified by the PDF specifications (a very long and detailed document), which can be found on Adobe's site: here.

Why was it created?

Before PDF was established in 1993, there was a clear lack of an easy way of sharing documents. A common way for many (only on Windows systems) was to share Microsoft Office .DOC files. However that format is not nearly as general (and has been known to change from time to time). The real strength of the PDF file is that it appears the same on all systems and is an open standard, so anyone can create a program that outputs PDF files.

Another format was the PostScript (PS) format, which actually has many things in common with the PDF format. It is still widely used in publishing and it is the native language for many printers. However, it never become very popular among the public, even though it was created long before the PDF format. Perhaps because that the PDF format was released and popularized in the relatively early days of the Internet. In addition the PDF format has many features over PS, such as being self-contained, containing all fonts, images, and so on in a single file. For interested readers, a comprehensive comparison between PS and PDF can be found here.

How does the future look?

The PDF standard has continually been upgraded since its initial release and many new features have been added. For example: password protection, interactive fill-in forms, digital signatures and multiple others. We can therefore expect to see many more features added in the years to come.

Recently the PDF standard has become an ISO (International Organization for Standardization) standard, and Adobe Systems is no longer responsible for maintaining it. Furthermore, in 2008 Adobe published a Public Patent License to ISO 32000-1, granting a royalty-free rights for all patents owned by Adobe that are necessary to make, use, sell and distribute PDF compliant implementations.


As an open and still evolving standard, it is likely that PDF will maintain its role as a leading document exchange format for (at least some) years to come.

Please share with us your view of the PDF format and how you think it's going to hold up in the future!

New webapps launched: Unlock PDF and Protect PDF

We have now launched our new webapps, UnlockPDF and ProtectPDF. As announced in our blog entry in September, we have been working hard to get the new services ready for launch.

The new services enable users to lock (add password protection) and unlock (remove password protection) from PDF files, and are a great addition to our already established suite of online PDF webapps.

Every day thousands of users merge and split PDF files, and we hope that many of our existing users will find the new additions useful.

As always, we encourage comments and bug reports, so feel free to leave us any feedback or bug reports in the comments or via e-mail.

Enjoy the new webapps!

Planned: Unlock PDF and Protect PDF

While we are working hard on improving our current services, Merge PDF and Split PDF, we are also planning to launch a couple of new services. We thank all our users who have given us valuable input in improving our services. We have submitted a lot of updates in the past few months. Please keep sending us bug reports when you encounter a failure, either through the comments or through email.

The new services will complement our other services, allowing users to remove passwords from PDF documents (UnlockPDF), as well as adding protection to their documents (ProtectPDF).

The PDF standard supports two kinds of passwords for each file. An owner password can be specified which allows adding protection such as limiting viewers' rights to print and/or edit the document and so forth. A user password is more restrictive as it requires a password to open the document.

UnlockPDF will be able to remove passwords from documents with owner passwords, even without specifying the password. However, for documents with user password, a password will be required to unlock pdf. It will also be possible to enter multiple passwords and our program will go through the list, trying each password until it finds the correct one. This will help if you do not remember exactly what password you used when the protection was added.

ProtectPDF, on the contrary, will allow users to add user and/or owner password to documents. The level of restrictions can also be specified, such as whether printing is allowed, and/or document edits, and so on.

If you have any suggestions for these planned services, please let us know and we will try to incorporate them, if possible!

Update: The services are now available and the links have been added in the above text.

About FoxyUtils

We specialize in creating and maintaining web apps for PDF.

Our current products are services to convert, merge, split, compress, lock and unlock PDF documents, see home page for a full list.