Mirror a PDF

Most tools mirror a PDF by turning each page into a picture, flipping the picture and wrapping it in a new PDF. The result looks right on screen and prints soft: the text is pixels now, at whatever resolution the tool chose. Transfer artwork is exactly the kind of file where that hurts — fine lettering, thin outlines, a cutter that follows vector edges.

A PDF page is a list of drawing instructions. This page adds one instruction in front of that list — reflect everything about the page’s centre line — and one after it to end the reflection. Every line, letter and curve is still drawn by the printer at its own resolution, just mirrored. The change is appended to your file as an update, the way a PDF editor saves, so the original pages are still inside it untouched. Pages turned in the file (rotated 90°) are mirrored the way they appear on screen.

1. 1Open the PDF. The artwork exported from your design app. It is read in this tab: pages, sizes, and anything that sits outside the page drawing.
2. 2Choose pages and axis. All pages, odd, even or a list like 1-3, 5. Left to right for nearly every transfer; top to bottom if your press loads from the far edge.
3. 3Read the warnings. Annotations and form fields are drawn separately from the page and are not mirrored; the page counts them before you save.
4. 4Save. The mirrored PDF downloads at once. Print it at 100 %, with the driver's mirror setting off.

A three-page A4 PDF of T-shirt artwork — 595 × 842 points per page, 210 × 297 mm — with only pages 1 and 3 chosen, left to right. Each chosen page gets the matrix [−1 0 0 1 595 0] in front of its drawing; the saved file is a few hundred bytes larger than the original, page 2 is untouched, and every page is still 210 × 297 mm. Opened in a PDF reader, the lettering on pages 1 and 3 is still selectable — it simply reads backwards.

• No page preview here. The page list shows each page's size and which way it will face, not its content. Open the saved file in a PDF reader to look at it.
• Annotations and form fields stay as they were. They sit outside the page drawing. Flatten them first if they must be mirrored.
• Password-protected files are refused. Save an unprotected copy from a PDF reader first.
• Unusual files may not open. A PDF this reader cannot follow is refused with the reason; saving it again from a PDF reader usually fixes it.

Does the text stay sharp?

Yes. Nothing is turned into a picture. Each mirrored page gets one instruction in front of its drawing — reflect about the centre — so text stays text, curves stay curves and the page prints at full printer resolution. The text even stays selectable and searchable; it simply reads backwards, like the page.

Does the page size change?

No. A4 stays A4 and Letter stays Letter. The reflection is about the page's own centre line, so nothing moves off the page.

What about form fields and comments?

They are drawn on top of the page separately, so a matrix in the page drawing does not reach them. The page counts them and warns you; flatten them in your PDF app first if they need to be mirrored too.

My PDF is password-protected.

This page opens only PDFs without a password. Open it in a PDF reader, save an unprotected copy, and open that. It does not try to get round a password.

Should I also mirror in the printer settings?

No — mirror in the file or in the driver, never both. Two reversals cancel. The file is the one you can check before you press.