Annotate PDF

No. A highlight is a see-through rectangle you drag over the words, not a selection of them. Flattened, it covers exactly the area you draw. Saved as a comment, it fits itself to the lines of text under the box: one band per line, as tall as the line and as wide as your box, the way a viewer's own text highlight looks. To hide text rather than mark it, use Redact PDF.

Saved as comments, yes: each highlight, drawing, note, shape and line is its own annotation, which a PDF app that edits comments can select and delete. Flattened, only with an editor that can change page content, because each markup is drawn into the page like ink rather than stored as a separate object. Before you apply, any markup can be selected and deleted, or undone, either way. Keep the original if you may want an unmarked copy.

Unless you turn, insert, delete or reorder pages in the page list, pages keep their count, size and rotation, and their text and images; the file keeps its bookmarks, form fields, existing annotations, title and author. What does change on an ordinary PDF: Creator and Producer both become this site's name, and an existing digital signature will no longer validate, because pdf-lib writes out a whole new file rather than appending to the signed one. A PDF whose author restricted changes is the exception: its original bytes are kept and the comments are appended after them, as an update under the author's own encryption. Markups sit on top of the page's own content, later ones over earlier ones.

No. The PDF is read, marked and saved by code running in this tab. The only files the tool itself fetches are pdf.xyz's own scripts and, when a note goes beyond the Western European character set, a Noto typeface from the /fonts/ folder on this same site: 137.8 KB for Bengali up to 10.1 MB for Chinese. That typeface is subset, so the finished PDF carries only the glyphs your notes use; notes in the built-in font embed no font file at all.

Not fully. The page and its processing engine load over the network, and parts of the engine are fetched the first time a step needs them. The processing itself runs on your device. Rendering a page that holds a JPEG 2000 or JBIG2 image, as scanned documents often do, downloads an image decoder from our site the first time it is needed, and that step needs a connection. Chinese, Japanese or Korean text whose font is not embedded in the PDF needs a character map, downloaded from our site the first time it is needed, and that step needs a connection. Drawing text in a script outside the Western European alphabet downloads a matching font from our site the first time it is needed, and that step needs a connection.

Up to 100 MB per file.

Not by default. Flatten into the page, the default beside Apply & download, draws Annotate PDF's highlights, freehand drawing and notes into the page itself, so a reader shows them as part of the page, not as comments. Choose Save markups as comments and they are written as standard PDF annotations instead, as are rectangles and ellipses, and lines and arrows: other PDF apps list them as comments and can select, edit or delete them. The whiteout boxes and redaction boxes that remove the text and picture pixels under them are always drawn into the page, because a comment can be deleted by whoever opens the file. On a PDF whose author restricted changes, markups are always saved as comments, and only if the author allows comments, until the owner password is entered.

Highlight is the tool the editor opens on: drag across the page where it goes, then drag its handles to fit. A highlight is a see-through box, so it tints whatever lies under it rather than following the words.