Portable Document Format
What is a PDF file?
PDF (Portable Document Format) was created by Adobe in 1993 and became an open ISO standard in 2008. A PDF stores every page exactly as it should look, with fonts, images and layout fixed in place, which is why contracts, forms, tickets and invoices are sent as PDFs. The trade-off is that PDFs are built for reading and printing, not editing.
How to open a PDF file
- Windows
- Double-click it: Microsoft Edge opens PDFs by default and can highlight, fill forms and add notes.
- Mac
- Double-click it to open in Preview, which also lets you sign, annotate, rotate and reorder pages.
- iPhone
- Tap it in Mail, Messages or the Files app; iOS shows it with the built-in viewer, and you can mark it up with the pen tool.
- Android
- Tap it in Files by Google or Gmail; it opens in the built-in PDF viewer or Google Drive.
Good for
- Looks identical on every screen and printer
- Can embed fonts, so nothing gets substituted
- Supports passwords, signatures and fillable forms
Watch out for
- Hard to edit text or tables directly
- Scanned PDFs contain pictures, not searchable text
- Large images can make files heavy to email
PDF file questions
Can I edit a PDF like a Word document?
Not directly. Convert it to Word first, make your changes, then save it as a PDF again if you need to send it.
Why can't I select the text in my PDF?
It's probably a scan, meaning each page is a picture. Run OCR on it to add real, selectable text.
How do I make a PDF smaller?
Most of the size is usually images. Compressing the PDF resamples them to a sensible resolution while keeping text sharp.