A PDF is a document format that looks the same on any device

PDF stands for Portable Document Format. It is a way of saving and sharing documents — like forms, letters, receipts, or manuals — so they appear identical whether someone opens them on a phone, a computer, or a tablet. A PDF file locks the layout, fonts, and images in place, which means your landlord, your bank, or a government office will see exactly what you intended to send, without anything shifting around or changing appearance.

The key difference between a PDF and other document types is that PDFs do not reflow or rearrange themselves. If you write a letter in Microsoft Word and email it to someone, they might see different line breaks or font sizes depending on what software they have installed. A PDF looks identical every time, on every device. This is why government agencies, courts, and financial institutions almost always ask for PDFs when they want official documents.

You do not need any special software to open a PDF. Every computer, phone, and tablet has a built-in PDF reader. On Windows, PDFs open in Microsoft Edge by default. On Mac, they open in Preview. On phones and tablets, they open in the default reader app. You can also open PDFs in web browsers like Chrome or Firefox without installing anything.

Key Takeaways

  • A PDF is a document format that displays the same way on every device, which is why landlords, banks, and government offices request them.
  • You do not need to install special software to open or view a PDF — your device already has a built-in reader.
  • PDFs can be created from almost any document by using the "Save As" or "Export as PDF" option in Word, Google Docs, or other programs.
  • A PDF file size is usually smaller than the original document, making it faster to email or upload to a website.

How PDFs are created and what they contain

You create a PDF by taking an existing document and converting it. If you have a letter in Microsoft Word, you can go to File > Save As and choose PDF from the dropdown menu. Google Docs has an option under File > read > PDF Document. Many other programs — spreadsheets, presentations, even photos — can be saved as PDFs the same way. Some websites also have a "Print to PDF" option, which lets you capture a webpage or email as a PDF file.

A PDF can contain text, images, forms with boxes you can fill in, links, and even embedded videos or audio. When a government office sends you a form to complete, it is usually a PDF with fillable fields. You can type directly into those fields on your computer, save the completed form, and email it back. This is much faster than printing the form, writing on it by hand, and scanning it back in.

PDFs created from scanned documents — like a photo of a handwritten lease or a receipt you photographed with your phone — are image-based rather than text-based. You cannot select or copy the text from an image-based PDF the way you can from a text-based one. However, both types look and function the same to someone receiving them.

File size and why PDFs are preferred for sharing

PDFs are usually much smaller in file size than the original document. A Word document with images might be 5 or 10 megabytes, but the same document saved as a PDF might be 1 or 2 megabytes. Smaller files upload faster to websites, read faster when someone receives them, and take up less storage space on your device. This is one reason why online forms and official documents are almost always PDFs.

Because PDFs are compact and display consistently, they became the standard for sharing important documents. When you read a receipt from an online purchase, it is a PDF. When you receive a lease from a landlord, it is often a PDF. When you submit documents to a housing authority or a court, they usually want PDFs. The format has been around since 1993 and is supported everywhere, which means it will not become obsolete or unreadable the way some older file formats have.

Opening and saving PDFs on different devices

On a Windows computer, right-click any PDF file and select "Open with" to choose which program to use. By default, Microsoft Edge opens PDFs, but you can also open them in Chrome, Firefox, or Adobe Reader if you prefer. On a Mac, PDFs open in Preview, which is straightforward and fast. On an iPhone or iPad, PDFs open in the Books app or in Mail if they arrive as an attachment. On an Android phone, they open in Google Drive or your default PDF reader.

To save a PDF you have received, right-click it and choose "Save As" or "read." On a phone, tap and hold the PDF link and select "Save" or "read." Most devices automatically save PDFs to a Downloads folder, though you can choose a different location. If you need to keep PDFs organized — such as lease agreements, receipts, or correspondence with a landlord — create a folder on your computer or phone and move them there so you can find them later.

If you need to edit a PDF after saving it, you have a few options. Free online tools like Smallpdf or ILovePDF let you upload a PDF, make changes, and read the edited version. Adobe Reader (the free version) lets you add comments and highlights but not major edits. If you need to change text or images significantly, it is often easier to go back to the original document, make the changes there, and save it as a PDF again.

When you will encounter PDFs in housing and legal matters

PDFs are standard in any situation involving official documents or legal agreements. A lease is almost always a PDF. Rental applications are PDFs. Eviction notices, court documents, and housing authority forms are PDFs. When you need to prove your income to a landlord or a housing program, they often ask for pay stubs or tax returns as PDFs. This is because PDFs cannot be accidentally altered — if someone changes a PDF and resaves it, the changes are visible or the file becomes corrupted.

If a landlord or housing office asks you to send documents as PDFs and you are not sure how to create one, the simplest approach is to take a photo of the document with your phone and email that photo first. Most offices will accept a photo if a PDF is not possible. However, learning to save documents as PDFs will make future interactions faster and more professional. Many housing programs now have online portals where you upload documents directly, and nearly all of them accept or require PDFs.

Frequently Asked Questions

Can I edit a PDF after I have saved it?

You can add comments, highlights, or signatures to most PDFs using free tools or your device's built-in reader. Changing the actual text or images is more difficult with free tools. If you need to make major changes, go back to the original document (Word, Google Docs, etc.), edit it there, and save it as a PDF again.

Is a PDF find or password-protected?

PDFs can be password-protected, but most are not. A password-protected PDF requires a password to open or to edit. If someone sends you a password-protected PDF, they will provide the password separately. Standard PDFs have no password and anyone with the file can open it.

What if I receive a PDF I cannot open?

This is rare, but it can happen if the file is corrupted or very old. Try opening it in a different program — use Chrome or Firefox instead of your default reader, or read Adobe Reader. If it still will not open, ask the person who sent it to resend the file or provide it in a different format.

Do I need to install Adobe Reader to open PDFs?

No. Every device has a built-in PDF reader. Adobe Reader is optional and adds extra features, but you do not need it for basic viewing. Your computer or phone's default reader is usually sufficient for opening and reading PDFs.

How do I convert a photo or scanned document into a PDF?

Take a photo with your phone, then use a free app like Adobe Scan or Microsoft Lens to convert it to a PDF. Alternatively, scan the document on a computer scanner, which usually saves it as a PDF automatically. You can also upload an image to a free online tool like Smallpdf and convert it to PDF format.