A watermark that marks the page without hiding the words.
Stamp DRAFT, CONFIDENTIAL or the recipient's name across every page. The balance is readability: too faint and it's ignored, too strong and nobody can read the document. The legibility meter tells you when you've crossed the line.
By default a watermark is a separate object on the page. Anyone with a PDF editor can select it and press delete. Flattening merges it into the page image, so removing it means repainting the page. Try removing each kind.
A generic CONFIDENTIAL stamp says the file is sensitive. A stamp with the reader's name says whose copy it was. People are far more careful forwarding a document with their own name across it. Add the list and we make one file per person.
Your browser builds q3-results.pdf as a real 12-page file. It then stamps it using the text, size, angle, colour, opacity, layout and pages from the studio above. The PDF standard offers four places to put a watermark. They look the same on screen, but they differ in size, in how easy they are to remove, and in what screen readers do with them.
/Artifact << /Type /Pagination /Subtype /Watermark >> BDCq /WM Do QEMC6 0 obj % Form XObject, written onceq/GS1 gs0.863 0.149 0.149 rgBT/FW 44 Tf0.707 0.707 -0.707 0.707 264.309 331.908 Tm (DRAFT) TjETQ
9 0 obj<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Resources << /Font << /F1 3 0 R >> /XObject << /WM 6 0 R >> >> /Contents [8 0 R 7 0 R] >>5 0 obj<< /Type /ExtGState /ca 0.18 /CA 0.18 >>
Stamps are centred using an average Helvetica Bold letter width, so very long or narrow text can sit a little off centre. A production stamper reads the real widths from the font's metrics.
The studio's opacity becomes /ca in a graphics state, and the viewer mixes the stamp colour into whatever is underneath. Below is that mix for your current colour and opacity, with the WCAG contrast ratio of the body text that results. The meter above is a rough guide; these numbers are exact.
% graphics state written into the PDF/GS1 << /ca 0.18 >>% ISO 32000-1 §11.3: for each channel% result = (1 − α)·B + α·Cα = 0.18 C = [0.86 0.15 0.15]paper B = [1.00 1.00 1.00] → [0.98 0.85 0.85] #f9d8d8text B = [0.16 0.15 0.13] → [0.16 0.15 0.13] (stamp is behind, text drawn after)% WCAG 2.2 contrast(L1 + 0.05) / (L2 + 0.05)= 15.03:1 before → 11.32:1 after
Click one to load it into the studio above.
The four methods above, plus the two you'll meet in other tools. Clause numbers refer to ISO 32000-1 (PDF 1.7).
PDF tools people use alongside this one.