What is a PDF used for?

A PDF is used whenever a document must look exactly the same for everyone: contracts, invoices, tickets, CVs, forms, manuals and official records. Because fonts and layout are stored inside the file, it prints and displays the same on any computer or phone, which is why many upload portals accept only PDF.

What does PDF stand for?

PDF stands for Portable Document Format. Adobe developed it in the early 1990s so documents could move between different computers and still look the same. Since 2008 it has been an open international standard, ISO 32000, maintained by ISO rather than by Adobe.

How do I open a PDF file?

Double click it. Windows 11 opens PDFs in Microsoft Edge, Macs use Preview, iPhones and iPads open them in Files or Books, and Android phones use a built in viewer or the Google Drive app. Any modern web browser on a computer can display a PDF as well.

You can add highlights, notes, signatures and form entries in most PDF viewers. Changing the main text is harder, because a PDF stores fixed pages. The best way is to edit the original Word or Google Docs file and save a new PDF, or convert the PDF to Word if the original is lost.

Is PDF better than Word?

For final documents, yes. A PDF keeps its layout, opens on every device without Word and is accepted by almost every upload portal. For drafts that other people need to change, a Word file is better because it is much easier to edit.

What Is a PDF? Meaning, How to Open It, PDF vs Word

A PDF is a file format that shows a document exactly the same way on every screen and printer. PDF stands for Portable Document Format, and that is what makes it the default for contracts, tickets, invoices and official forms: the fonts, images and page layout all travel inside the file.

Below you will find what a PDF really is, where it came from, how to open one on any device and when a PDF is a better choice than a Word document.

What is a PDF? The meaning in plain words

Think of a PDF as a digital sheet of paper. When you create one, every page is fixed: the text, the line breaks, the pictures and the margins are locked in place. Whoever opens the file sees the pages the way you saw them, even without your fonts or your software.

A Word document works differently. It stores text and styling instructions, and the program that opens it lays out the pages again. A different version of Word, a missing font or another paper size can move a line or push a table onto the next page.

A PDF does not have that problem. That is why schools, banks, courts, airlines and employers ask for it when the content must arrive exactly as it was sent.

What PDF stands for

PDF stands for Portable Document Format. Portable means the file carries everything it needs to be displayed. Document format means it describes finished pages rather than an editable draft. The file extension is .pdf, and the file type is often shown as "PDF Document" or "Adobe Acrobat Document" on Windows.

Merge PDF

Combine several PDFs into one file, in any order. Free, no signup.

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A short history: from Adobe to an open ISO standard

PDF began at Adobe. In 1991, Adobe cofounder John Warnock wrote a proposal called the Camelot project. His goal: anyone should be able to send a document from one computer to another and view or print it exactly as it was made, no matter which system they used.

Adobe released the first version of PDF in 1993, together with its Acrobat software. Adobe published the specification so other companies could build PDF readers and writers, and later made its Reader app free. Over the years PDF spread to practically every office, school and government in the world.

In 2008 PDF became an open international standard, ISO 32000 part 1, based on PDF 1.7. Since then the format has been maintained by the International Organization for Standardization (ISO), not by a single company. PDF 2.0 followed as ISO 32000 part 2 in 2017, and a corrected second edition of PDF 2.0 was published in 2020.

There are also specialized versions for specific jobs. PDF/A is made for long term archiving, PDF/X for professional printing, and PDF/UA for documents that work well with screen readers.

What can be inside a PDF file

A PDF can be a one page receipt or a 900 page manual. Inside, it can hold:

Text and fonts. Fonts are usually embedded, so letters look right everywhere. Text in a normal PDF can be selected, copied and searched.
Images and vector graphics. Photos, logos, charts and drawings. Vector parts stay sharp however far you zoom in.
Links and bookmarks. Clickable web links, a table of contents in the sidebar and jumps between pages.
Fillable forms. Text boxes, checkboxes and dropdown lists you can fill in on screen.
Security. An open password, restrictions on printing or copying, and digital signatures that show who signed a document and whether it changed afterwards.
Attachments and comments. Other files tucked inside, plus highlights, sticky notes and stamps.

Digital PDFs and scanned PDFs

Not every PDF has real text inside. A PDF made from Word, a web page or an accounting app contains actual letters you can search. A PDF made by a scanner or a phone scanning app is often only pictures of pages.

Both look the same on screen. In a scanned PDF, though, you cannot select a word or search for a name. Turning it into editable text needs OCR (optical character recognition), a step that reads the letters from the image.

How to open a PDF on any device

You rarely need to install anything. Every major system has a PDF viewer built in, and every modern web browser can display PDFs too.

Windows 11

Double click the file. Windows 11 opens PDFs in Microsoft Edge by default, where you can read, print, highlight, draw and fill in simple forms. If another app has taken over, right click the file, choose Open with and pick Microsoft Edge or another PDF reader. Adobe Acrobat Reader is a free download if you need more tools.

Mac

PDFs open in Preview, which can highlight, sign, fill in forms, reorder pages and export. To peek at a PDF without opening an app, select it in Finder and press the Space bar.

iPhone and iPad

Tap a PDF in Mail, Messages or the Files app and it opens in a viewer with Markup tools for drawing, highlighting and signing. To keep a PDF for later reading, tap the Share button and choose Books.

Android

Most Android phones open PDFs with a built in viewer, usually from Google Drive or the phone maker's file app. Which one you see depends on the brand and the Android version. If a PDF will not open, install the free Google Drive app and open the file from there.

On a computer, you can also drag a PDF into a Chrome, Edge, Firefox or Safari window and it opens in a tab.

PDF vs Word: which one should you send?

Both formats have a place. A good rule: send Word when someone needs to edit the text, send PDF when someone needs to read, print, file or sign it.

Feature	PDF	Word (DOCX)
Looks the same everywhere	Yes, pages are fixed	Not always, layout can shift
Easy to edit	Limited, needs a PDF editor	Yes, in Word or Google Docs
Opens without extra software	Yes, in browsers and built in viewers	Needs Word or a compatible app
Fillable forms and signatures	Yes	Limited
Accepted by upload portals	Almost always	Sometimes
Best for	Final versions, forms, printing, archives	Drafts and shared editing

Why PDFs are hard to edit

A PDF stores positioned pieces of text, not flowing paragraphs. When you change a sentence, the rest of the paragraph does not move along the way it does in Word. That is a feature for final documents and a nuisance for drafts.

The fix is to edit the source and make a fresh PDF. Our guide on saving a Word document as a PDF walks through it. When the original is gone, PDF to Word pulls the text of every page into an editable DOCX file, although the exact layout, images and tables are not kept.

How to make a PDF and work with it

Save any document as a PDF

Every device can save a PDF without extra apps:

Windows: in almost any app, press Ctrl + P and choose Microsoft Print to PDF as the printer.
Mac: choose File > Export as PDF where the app offers it, or open the Print dialog and pick Save as PDF from the PDF menu.
iPhone and iPad: in the Files app, select one or more images or PDFs, tap the More button and choose Create PDF. The Notes app can also scan paper documents to PDF.
Android: open the Print option in an app's menu and choose Save as PDF as the printer.
Office apps: Word, Excel and PowerPoint save directly as PDF from File, then Save As or Save a Copy.

Combine and trim PDFs in your browser with FileKiwi

Once a document is a PDF, the usual next jobs are combining, trimming and shrinking it. FileKiwi has free tools for these that run in any modern browser on a computer or phone.

Open Merge PDF and add up to 50 PDF files.
Drag the files into the order you want.
Click Merge and download one combined PDF. Pages are copied as they are, so quality and page sizes do not change.

The full set of PDF tools also covers splitting, rotating, deleting pages, page numbers, watermarks and passwords. A copy of each file you add is kept in a private folder for 30 days and then deleted, and the finished files are not stored.

Common PDF problems and how to fix them

The file is too large to upload or email. Compress it. Our guide on how to compress a PDF explains the levels and what they do to images.
The PDF asks for a password. You need the password from the sender. Without it nobody can open the file, which is the point of the protection.
You cannot select or search the text. It is probably a scanned PDF that holds pictures of pages. It needs OCR before the text can be edited.
Pages are sideways. Rotate them in the viewer to read, then save a rotated copy so the next person does not have to.
A form loses your answers. Some phone viewers display forms but do not save typed values. Try Edge, Preview or Acrobat Reader instead.

Are PDF files safe to open?

A PDF can contain links, attachments and scripts, and attackers sometimes hide malware in fake invoices or delivery notices. Open PDFs only from senders you trust, keep your browser and PDF reader updated, and be careful with links inside a PDF that ask you to log in.

When to choose PDF

Choose PDF for anything final: a CV, a signed contract, an invoice, a form you must submit or a document someone will print. Keep the Word or Google Docs original for later changes, and make a new PDF after each edit.

For records that must last many years, check whether the archive or court wants the PDF/A variant. For everyday sharing, a normal PDF opened in the built in viewer on any device does the job.

What Is a PDF? Meaning, History and How to Open One