Why Annotate PDFs on iPhone
Review a contract on your commute—highlight the clause that needs revision. Read a report in a coffee shop—circle the key findings. Grade student papers on your couch—mark corrections directly on submissions.
PDF annotation on iPhone means your markup tools are always in your pocket. No need to print, no need to wait until you're at your desk. Review and annotate whenever inspiration (or deadline) strikes.
Annotated PDFs share like any other PDF. Send marked-up documents via email, drop them in shared folders, or upload to collaboration platforms. Recipients see your annotations in any PDF reader—no special software required.
Annotation also sits in the middle of several adjacent workflows: sign the reviewed version, apply a draft or review watermark, or merge marked pages into a larger packet once comments are complete.
Apple Pencil Support for Precise Annotation
ScanLens annotation is powered by Apple PencilKit, providing professional-grade drawing capabilities:
Pressure Sensitivity
Press harder for thicker strokes, lighter for thin lines. Natural handwriting feel that responds to your pressure just like pen on paper. Write naturally, get beautiful results.
Tilt Recognition
Angle your Apple Pencil to shade large areas quickly with highlighter. Upright for precision, tilted for coverage. The same techniques you use with real art supplies.
Palm Rejection
Rest your hand naturally on the screen while drawing. ScanLens ignores palm contact and only registers Apple Pencil input. Write comfortably without worrying about accidental marks.
Low Latency
Ink appears instantly as you draw—no lag between pencil movement and screen response. The immediate feedback makes annotation feel natural and responsive.
Annotate with Your Finger
No Apple Pencil? No problem. All annotation tools work perfectly with finger input on any iPhone or iPad:
Touch-Optimized Controls
Large touch targets for tool selection and color picking. Easy to use even on smaller iPhone screens. No precision stylus required for basic markup.
Zoom for Precision
Pinch to zoom into documents for detailed annotation areas. Draw fine details at high zoom, then zoom out to see the full page. Precision through magnification.
Quick Highlights
Swipe with highlighter tool to mark important text. Large finger strokes work well for highlighting—the semi-transparent color covers text cleanly.
Beyond pen and highlighter: text, shapes, stamps, and signatures
The pen and highlighter cover emphasis and freehand notes, but the markup toolbox goes further. The full set lives in one menu — Marker, Highlighter, Eraser, Shapes, Stamps, Text, Signature, and Watermark — so you switch modes without leaving the page. These are the tools that turn simple highlighting into real document review.
Text boxes
Typed text dropped anywhere you tap, with adjustable size and color, draggable after you type it. Where handwriting is messy or a recipient expects legible comments, a text box is clearer. Label parts of a diagram, leave a typed margin note, or write a name and date onto a flat form. Text boxes and ink are independent layers — mix them freely on the same page.
Shapes
Rectangles, circles, lines, and arrows with control over color, line width, and fill. Box a figure in a report, draw an arrow to the change you want, or ring an answer on a worksheet. Shapes snap to clean geometry rather than relying on a steady hand, which reads as more deliberate than a freehand scribble in formal review.
Stamps
Tap-to-place marks for repeated symbols — checkmarks and crosses for tick-boxes, and reusable graphic stamps. A stamp drops in one tap and scales to the page, so marking many boxes or pages is fast. Stamps pair naturally with the form-fill workflow when you are ticking options on a flat PDF.
Signature
Draw your signature once and ScanLens saves it; after that, signing any document is tap-and-place. Keep several saved signatures — full name, initials, an alternate — and pick the right one per document. For the complete signing workflow, including dates and multi-party documents, see sign PDF on iPhone.
Annotate vs fill a form vs edit — which tool is the right one?
Three PDF jobs get confused because they all happen "on top of" a document, but they are distinct tasks. Knowing which you need saves a lot of fiddling.
Annotate means marking up a page visually: highlighting text, drawing ink, adding shapes, stamps, and text-box comments. The page content stays as it was; you add a layer of commentary over it. This is the tool for proofreading, redlining a contract, marking a diagram, or leaving feedback — anything where your marks comment on content that already exists.
Filling a form is a focused subset: positioning typed text into fields, ticking boxes with checkmark stamps, dropping a signature on the line. The goal is to complete a document rather than comment on it. For a job application, permission slip, or intake form, the form-fill workflow is framed around exactly that — including the distinction between flat PDFs (which ScanLens fills) and interactive AcroForms (which need a desktop filler).
Editing changes the document's structure rather than its surface — reordering or deleting pages, merging, splitting, compressing, rotating. Those change which pages exist and in what order, not what is drawn on them; the PDF editing hub is the right page. Rule of thumb: adding marks is annotating, completing fields is filling, changing the pages themselves is editing.
