Skip to content
PDFinish

What is a PDF?

By the PDFinish editorial team · Reviewed · Published · 6 min read

Last updated:

A PDF, short for Portable Document Format, is a file format that keeps a document looking the same on any computer, phone or printer. Adobe created it, and since 2008 it has also been an open international standard, ISO 32000.

PDF at a glance

PDF in seven facts

QuestionAnswerSource
What PDF stands forPortable Document Format. Most people just say "PDF".Adobe
Who created itAdobe. Co-founder John Warnock started the Camelot Project in 1991, and Adobe says it had become PDF by 1992.Adobe
First releasePDF 1.0, June 1993, together with Acrobat 1.0.Library of Congress, PDF 1.0 to 1.3
Current standardISO 32000-2 (PDF 2.0), published as the 2017 edition and revised in December 2020.Library of Congress, PDF 2.0
File extension.pdfLibrary of Congress, PDF 1.4
Media typeapplication/pdf, registered with IANA.Library of Congress, PDF 1.4
Open standard sinceJuly 2008, when PDF 1.7 was published as ISO 32000-1.Library of Congress, PDF 1.7

For the full story of every version and the years behind these facts, read PDF history and versions.

Why PDF exists

Adobe describes the goal of its early work as letting anyone capture a document from any application, send it anywhere and view and print it on any machine. That is the "portable" in the name: the page you made is the page everyone else sees, whatever software, hardware or operating system they use.

How a PDF works

The Library of Congress describes a PDF as a page-oriented document that can hold text, images, graphics and other content, with support for annotations, metadata, hypertext links and bookmarks. In plain words, a PDF is a box of pages with some extras attached. Here are the parts you will meet most often.

  • Pages. Each page is a fixed drawing. Text, lines and pictures sit where the author put them, so a long contract does not reflow when you open it on a phone. To change the order or number of pages, you can merge PDF files or split a PDF. PDFinish does this in a current browser on Windows, Mac or a phone; see PDFinish on Windows, Mac and phones.
  • Fonts. The letters on a page are drawn with fonts. A PDF can carry its fonts inside the file, which is why it looks the same on a computer that does not have them. Compress a PDF when embedded fonts and images make the file too big to email.
  • Images. Photos and scans are stored inside the file. If you need them out, extract images from a PDF or convert a PDF to JPG.
  • Text layer or just a picture. Many PDFs are simply pictures of pages, as Adobe notes. A PDF made from a word processor has real, selectable text. A scan has only a picture until a text layer is added, which is what making a scanned PDF searchable does. You can also copy text out of a PDF.
  • Form fields. Some PDFs have boxes you can type in. You can fill in a PDF form in your browser, or create a fillable PDF of your own. When the answers are merged into the page, you have a flattened PDF, and the Flatten PDF tool does that.
  • Comments and marks. Highlights, notes and stamps are called annotations. You can annotate a PDF without changing the page underneath.
  • Signatures. A signature in a PDF can be a picture of your handwriting, or a certificate-based digital signature that can be checked cryptographically. They are different things. Sign PDF places a picture of your signature, not a certificate-based digital signature.
  • Passwords. A PDF can be locked so it needs a password to open. You can password-protect a PDF, and if you know the password you can unlock a PDF you own.
  • Bookmarks. The clickable outline in the side panel of a long PDF is made of bookmarks. You can add bookmarks to a PDF to make a long file easier to navigate.
  • Hidden content and redaction. Covering a word with a black box does not always remove it. To remove sensitive text for good, redact a PDF.
  • Size. Scans and photos make PDFs large. Smaller files send faster, and a PDF reader opens them without any other software.

Want to edit the words themselves? The PDF Editor tool adds text and shapes to a page.

Is PDF open and free to use?

Yes, in the way that matters to most people. Adobe says the PDF format is now an open standard maintained by the International Organization for Standardization (ISO). The first ISO edition was PDF 1.7, published as ISO 32000-1 in July 2008, and the current one is ISO 32000-2 (PDF 2.0).

The PDF family: PDF/A, PDF/X, PDF/UA, PDF/E and PDF/VT

Some jobs need a stricter kind of PDF. These special-purpose standards each limit what a PDF may contain so that every program treats it the same way. They are explained in more detail, with their ISO numbers and years, on the PDF history and versions page.

  • PDF/A is for long-term preservation. All fonts must be embedded and encryption is not allowed. See the PDF/A standards and their years.
  • PDF/X is for sending files to a commercial printer, so the print comes out as designed.
  • PDF/UA is for accessibility, so screen readers can read the document in order.
  • PDF/E is for engineering documents, with 2D and 3D drawings.
  • PDF/VT is for variable data printing, such as mailings where each copy differs.

Where PDFinish fits

PDFinish is a set of PDF tools that run in your browser, so your files stay on your device for most jobs. Start with the PDF reader, or browse every tool on the home page. PDFinish is a separate company from Adobe and is not affiliated with it.

Questions people ask

What does PDF stand for?

PDF stands for Portable Document Format. Adobe created it so that a document would look the same on any device and operating system.

Who invented the PDF?

Adobe created PDF. Adobe says its co-founder John Warnock launched the Camelot Project in 1991 and that the project had developed into PDF by 1992. The first specification, PDF 1.0, is dated June 1993.

Is PDF an open standard?

Yes. PDF 1.7 was published as ISO 32000-1 in July 2008, and the current edition is ISO 32000-2 (PDF 2.0), published in 2017 and revised in December 2020.

What is the file extension for a PDF?

The extension is .pdf and the media type is application/pdf.

Is a PDF a picture?

Sometimes. Many PDFs are simply pictures of pages, such as scans. Others have real, selectable text. A scanned PDF can be made searchable by adding a text layer.

What is the difference between PDF and PDF/A?

PDF/A is a stricter form of PDF made for long-term preservation. It requires all fonts to be embedded and forbids encryption, audio, video and JavaScript in its first version.

What is the latest PDF version?

PDF 2.0, which is ISO 32000-2. The 2017 edition was revised in December 2020, as of the Library of Congress page we read on October 27, 2026.

Is a signature in a PDF the same as a digital signature?

No. A signature picture is an image placed on the page. A certificate-based digital signature can be checked cryptographically. PDFinish's Sign PDF places a picture of your signature.

Sources

Every date and version on this page comes from the pages below, which we read on . Facts we could not confirm on one of them are left out.

PDFinish is not affiliated with Adobe or the other organizations named here. Pages are written in our own words; see how we write and check them in the editorial policy.