PDF basics

Start here. These three answer the questions everything else assumes you already know — what the format is, what is inside a file, and which format to send.

What a PDF file actually isWhat is a PDF, underneath?A PDF describes finished pages, not editable text. What is inside the file, why it looks the same everywhere, and what that costs you.
Is this PDF scanned or is it text?How can I tell whether a PDF is scanned?A scanned PDF is a photograph of a page. How to tell in two seconds, why it changes what every tool can do, and what OCR fixes.
PDF or Word: which should you send?Should I send this as a PDF or as a Word document?Send a PDF when the layout must survive the trip, and a Word file when someone has to change it. What each format guarantees, and what it costs.
How to edit a PDFHow do I edit a PDF?"Edit a PDF" means five different jobs, and they need different tools. Work out which one you have first.
What PDF/A is, and why an archive rejects an ordinary PDFWhat is PDF/A, and why was my PDF rejected?PDF/A is a PDF that must carry everything it needs inside itself. What the standard forbids, and how to tell whether a file really is one.

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