What Is a PDF, and Why Did It Become the Standard for Documents?

PDF stands for Portable Document Format. Adobe introduced it in 1993 with a simple aim: a document should look the same on every computer, printer and screen, whatever fonts or software are installed.

The problem PDF solved

Before PDF, sending a document usually meant sending a word-processor file. On the recipient's computer, missing fonts changed the layout, margins shifted and page breaks moved. A PDF stores the page as it should appear, including fonts, images and positioning, so it looks the same everywhere.

An open standard

PDF began as a proprietary format, but in 2008 it was published as an international standard (ISO 32000), which means many different programs can create and open PDFs. That is a big reason it's supported on nearly every phone, computer and browser.

What's inside a PDF

A PDF can contain:

• Text, with embedded fonts
• Images and graphics
• Multiple pages
• Links and bookmarks
• Form fields
• Metadata, such as title and author
• Security settings, such as passwords

Scanned PDFs versus text PDFs

This difference matters:

• Text-based PDF: created from a digital document. The text is real text, so you can select, copy and search it.
• Scanned PDF: each page is a picture of paper. It looks like a document, but the computer sees only an image, so you usually can't select or search the words, unless special text recognition is applied.

A document scanner app produces scanned PDFs: reliable copies of what's on the paper.

Why PDF suits scans

• One file for many pages. A ten-page contract becomes one document.
• Consistent look. The recipient sees your scan the way you do.
• Easy to share. Email, messaging apps and cloud storage all handle PDFs.
• Print-ready. Pages keep their proportions when printed.
• Compressible. File size can be reduced for sending.

PDF versus image files

An image file such as JPG is fine for a single photo, but PDFs are better for multi-page documents and anything to be printed or filed.

Reading PDFs

Every modern phone can open PDFs, and a scanner app with a built-in PDF reader lets you view your scans and other PDFs without needing another app.

Limits of PDFs

• They're not designed for easy editing.
• Scanned PDFs can be large.
• Some old PDFs rely on fonts or features that display poorly on very small screens.

A useful habit

When you get a PDF, note whether the words can be selected. If they can, it's text-based; if not, it's a scan.

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