Feedback on a build used to arrive as an email describing a spacing issue in words, which meant guessing exactly what pixel the designer meant. Now we export the current build as a PDF, and designers mark it up directly with notes and red circles before sending it back.
It sounds like a small change but the difference in review speed is real. A marked-up PDF removes almost all ambiguity about which element and what exact change is being requested, compared to a paragraph starting with "the spacing near the top feels off," which could mean any of four or five different things depending on which element the designer actually means.
Why this specific format works
PDFs are something every designer we work with already knows how to annotate, most design software can export a comp or a screenshot directly to PDF, and basic markup tools, the kind built into a PDF reader, are familiar enough that we're not asking anyone to learn a new tool just to give us feedback. That familiarity matters more than it might seem, a sophisticated feedback tool that requires training is worse in practice than a simple format everyone already knows, if the simple format solves the actual problem.
What actually changed in practice
Review cycles that used to take three or four emails back and forth, "what part exactly," "the header," "which part of the header," now typically resolve in one round. We're seeing roughly half the calendar time between "here's a build for review" and "approved, ship it," across the handful of projects we've measured this informally on, mostly because there's no clarifying-question round trip anymore, the markup itself is the clarifying information.
What we're still looking at
We're looking at whether there's a browser-based tool that does this more directly, letting a designer click directly on the live build and leave a comment pinned to that exact element, rather than exporting a static PDF of a moment-in-time screenshot that might already be slightly out of date by the time it's reviewed. Nothing we've found yet feels mature enough to switch to, but for now, PDF plus a red pen beats email threads by a wide margin, and that's a genuinely good place to be compared to where we started the year.
We've also started asking designers to number each piece of feedback on the PDF directly, then reply to us listing which numbers are addressed once we've made the change, rather than us guessing whether a fix actually covers everything they flagged. It's a small addition but it's closed the loop on the handful of review rounds where something got missed simply because it was one comment among a dozen others on a busy page.