# Introduction to PDF Course: [PDF](https://www.devtutorials.ai/learn/pdf) ยท Section: Getting Started Source: https://www.devtutorials.ai/learn/pdf/getting-started/introduction-to-pdf > What a PDF is, how it differs from Word files and photos, why people share documents as PDF, and where you'll meet PDFs every day. Bank statements, school reports, train tickets, user manuals, job application forms: open almost any important document someone sends you, and there's a good chance it's a **PDF**. In this lesson, you'll find out what a PDF is, what makes it different from a Word file or a photo, why people choose it for sharing, and where you'll meet it every day. Then you'll open your first PDF in the sandbox and find information in it. ## What is PDF? **PDF** stands for **Portable Document Format**. It's a file format for documents that must look **exactly the same** wherever they're opened: on a Windows laptop, a Mac, an iPhone, an Android tablet, or a printer in another country. The name says what it does: | Word | Meaning | |---|---| | **Portable** | The file can travel anywhere and still look right, on any device, without the program that made it | | **Document** | It's built for pages: text, pictures, tables, and page numbers in fixed positions | | **Format** | It's a standard way of saving a document so PDF apps can open it | A PDF file ends in `.pdf`, like `Invoice INV-2048.pdf`. Adobe created PDF in 1993. Since 2008, the PDF format has also been an **open standard**, which means anyone is free to build an app that reads or creates PDFs. That's why every phone, computer, and web browser can open one today. You don't need any PDF software installed to follow this course. Every lesson has a **PDF sandbox**: a full PDF viewer that runs inside this page. Open it with the **Open the PDF sandbox** button at the bottom-right, or press **Ctrl + backtick** (Cmd + backtick on Mac). What you learn there works the same way in Adobe Acrobat Reader, Microsoft Edge, Chrome, and other PDF apps. Now that you know what a PDF is, the next step is understanding how it differs from the other file types you already use. ## How a PDF is different The easiest way to understand PDF is to compare it with the files you already know: | | **Word document** (.docx) | **Photo or scan** (.jpg, .png) | **PDF** (.pdf) | |---|---|---|---| | Looks the same everywhere | No: fonts and layout can shift between computers | Yes | **Yes** | | Text can be selected and searched | Yes | No: it's just a picture of text | **Yes** (unless it's a scan) | | Easy to edit | Yes: that's its job | No | **Not easily**: it's meant to be read | | Several pages in one file | Yes | No: one picture per page | **Yes** | | Fillable forms and signatures | Limited | No | **Yes** | Think of it like this: a **Word file** is a document that's still being written. A **PDF** is the finished, printed version, but on screen. You *write* in Word; you *share* as PDF. You can make a PDF from almost any program: in Word, Excel, or PowerPoint, choose **File** > **Save As** (or **Export**) and pick **PDF**. On any computer, printing to **Save as PDF** or **Microsoft Print to PDF** works too. PDFs can contain more than fixed pages. They can also include links, comments, and form fields. ## Features of PDF files A PDF can hold much more than text on a page: - **Text and fonts**: the fonts are stored **inside** the file, so the text looks right even on a computer that doesn't have them. - **Pictures, shapes, and tables**, each fixed in its exact place. - **Bookmarks**: a clickable table of contents in a side panel, for jumping around long documents. - **Links**: to websites, or to other pages in the same PDF. - **Form fields**: boxes you can type into, tick boxes, and drop-down lists. - **Comments and markup**: sticky notes, highlights, and drawings that reviewers add on top of the page. - **Signatures**: drawn, typed, or certified digital signatures. - **Security**: a password to open the file, or limits on printing, copying, and editing. You'll use every one of these in this course. ## Advantages of PDF: why use it? ### Preserves document formatting When you send a Word file, the reader's computer rebuilds the page with **its own** fonts and settings. Lines can wrap differently, pictures can jump to the next page, and a two-page letter can become three. A PDF stores the page **as it was laid out**, so page 4 is page 4 for everyone, and a table never breaks in the middle. ### Easy to share PDFs are usually small enough to email, and anyone can open them for free: every web browser has a built-in PDF viewer. You never have to ask "Do you have the right program?" ### Works across devices The same file reads the same on a phone, a tablet, a laptop, and paper. That's what *portable* means: the page looks the same wherever it's opened. It also prints exactly as it looks on screen. ### Secure document distribution A PDF can be **locked** with a password, set so that it can't be printed or copied, and **digitally signed** so that anyone can check who sent it and that nobody changed it afterwards. Because a PDF is hard to edit by accident, it's also safer for documents where the numbers matter, like invoices and contracts. PDF is the format for **finished** documents. Keep the original Word, Excel, or PowerPoint file for editing, and create a PDF when it's time to share, print, or archive. Now that you've seen what PDFs can do and why people use them, let's look at some common situations where PDFs are used every day. ## Common uses of PDF | Use | Examples | Why PDF? | |---|---|---| | **Reports and documents** | Annual reports, school reports, research papers, user manuals | Charts, tables, and page numbers stay in place over many pages | | **E-books** | Guides, textbooks, magazines, recipe books | Bookmarks and links make long documents easy to move around | | **Forms** | Job applications, tax forms, membership forms | Fillable fields can be typed into, saved, and printed | | **Invoices** | Bills, receipts, quotes, purchase orders | The totals can't be changed by accident, and it prints on one page | | **Official documents** | Letters from councils and banks, certificates, contracts, tickets | Looks official, can carry a trusted digital signature | A few simple habits can help you get the most from PDF files and avoid common problems. ## Common mistakes | Mistake | What happens | How to fix it | |---|---|---| | Trying to edit a PDF like a Word file | The text won't change, or the layout breaks | Edit the original file, then make a new PDF | | Sending a photo of a document | It's blurry, can't be searched, and prints badly | Scan or save it as a PDF instead | | Expecting a scanned PDF to be searchable | Search finds nothing: the page is a picture | Use a scanned PDF's OCR (text recognition) feature, or ask for the original | | Sending the editable original by mistake | Others change your numbers or see tracked changes | Send the PDF and keep the original yourself | | Thinking PDF means "secure" | Anyone can still forward an unprotected PDF | Add a password or permissions when it matters (Chapter 6) | ## Exercise Here is your first chance to work with a real PDF. Click **Open the practice PDF** below. It opens **PDF Basics**, a short file with one example of each kind of everyday PDF, in the sandbox. Each task asks you to find something in it: type the answer in the box and press **Check**. You'll learn every button properly in the next lesson; for now, use the arrows at the top of the viewer to move between pages. ## What to remember - **PDF** = **Portable Document Format**: a file that looks the same on every device and printer. - Fonts, pictures, and layout are stored **inside** the file, so the page can't shift. - **Write** in Word, Excel, or PowerPoint; **share** as PDF. Keep the original for changes. - PDFs can hold **bookmarks**, **links**, **forms**, **comments**, **signatures**, and **security**. - Everyday uses: **reports**, **e-books**, **forms**, **invoices**, and **official documents**. - A **scanned** PDF is a picture of a page: you can't search or select its text without OCR. In the next lesson, you'll take a tour of the PDF viewer: the toolbar, the navigation pane, zoom, search, print, and download.