The flyer looks right on the designer’s laptop. At the print supplier, a heading wraps differently and a symbol changes shape. Opening a PDF successfully does not prove that every font needed to reproduce it is contained in the file.
Adobe’s guidance on embedding and substitution explains that embedding helps prevent another font being substituted. A font may be fully embedded or included as a subset containing the characters used. Licensing and export settings affect what is possible.
Check the delivery file, not only the source document
Inspect the fonts listed in the exported PDF using the application’s document properties or preflight tools. Look for the embedding status and any warnings. Then compare the exported pages with the approved design, paying attention to line breaks, special characters and small labels.
Ask the printer for its required PDF specification before the final export. Do not assume that a setting suitable for a lightweight email attachment is also the right setting for print production.
Keep optimisation from undoing the handover
Adobe’s PDF optimisation documentation includes font-unembedding options as well as image compression. Reducing file size can therefore change more than the photographs. Retain an approved master and check the optimised version before sending it.
If a font cannot be embedded, resolve that issue with the designer, font supplier and printer. Replacing the font or converting text to outlines can have consequences for appearance, accessibility and later editing. Neither should happen silently at the last minute.
Include a clear version name with the final PDF and obtain a proof through the agreed print process. The goal is a file whose appearance can be reproduced reliably, not merely one that opens without an error on the machine that created it.