What you should know
PDF (Portable Document Format) was published by Adobe in 1993 so a document displays the same way everywhere. It describes each page as a fixed image: positions, fonts and graphics are embedded in the file.
Standardised as ISO in 2008, it is now the exchange format for contracts, invoices, theses and forms. Its rigidity is its quality: what you see is what everyone will see, on paper and on screen.
Strengths
- Fixed layout, identical on every device and in print
- Fonts and images embedded in the file
- Electronic signatures and password protection supported
- Text search and copy possible when the document contains text rather than an image
Limitations to know
- Hard to edit without specialised tools: it is not an editing format
- A scanned PDF is just an image: text is not selectable without OCR
- Heavy files (high-definition images) are awkward to email
- May contain forms and JavaScript, with the associated risks
When to use it
Produce a PDF to share a document whose layout must stay intact, to sign or to archive. To change the content, go back to the source format when it exists, or use an editor that manipulates pages.
Quality, size and compatibility
Converting a document to PDF embeds fonts and freezes layout: the file grows slightly but loses nothing. From PDF to a text format, everything depends on the document: a software-generated PDF yields clean text, a scan requires character recognition.
Frequently asked questions
- Why is my scanned PDF not editable?
- Because it contains an image of the page, not text. It needs optical character recognition (OCR) to produce selectable text.
- How do I reduce a PDF's size?
- The cause is almost always images. Recompressing them as JPEG at reasonable quality, or lowering their resolution, halves the file without blurring the text — since text stays vector-based.