> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chromiumly.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# PDF engines overview

> Convert to PDF/A and PDF/UA, merge, watermark/stamp, read/write metadata and bookmarks, split, rotate, and flatten PDFs with PDFEngines.

The `PDFEngines` class uses Gotenberg’s [PDF Engines routes](https://gotenberg.dev/docs/manipulate-pdfs/pdfa-pdfua) to manipulate existing PDFs. It does not create PDFs from HTML or URLs; use the [Chromium](/chromium/overview) or [LibreOffice](/libreoffice) routes for that. Merge order is **alphanumeric** by filename (same as Gotenberg).

## Operations

| Method           | Description                                                       |
| ---------------- | ----------------------------------------------------------------- |
| `convert`        | Convert PDFs to PDF/A and/or PDF/UA                               |
| `merge`          | Merge multiple PDFs into one                                      |
| `watermark`      | Apply watermark overlays behind page content                      |
| `stamp`          | Apply stamp overlays on top of page content                       |
| `readMetadata`   | Read metadata from PDFs                                           |
| `writeMetadata`  | Write metadata to PDFs                                            |
| `readBookmarks`  | Read PDF bookmarks (document outline)                             |
| `writeBookmarks` | Write PDF bookmarks (document outline)                            |
| `split`          | Split PDFs by page ranges or intervals                            |
| `rotate`         | Rotate pages of existing PDFs                                     |
| `flatten`        | Flatten forms and annotations                                     |
| `generate`       | Helper to write a buffer to a file (e.g. `__generated__/out.pdf`) |

All methods accept `files` as an array of paths or `{ data, ext }` objects. See the individual pages for parameters and examples.

## Next pages

* [Convert](/pdf-engines/convert) — PDF/A and PDF/UA
* [Merge](/pdf-engines/merge)
* [Watermark and stamp](/pdf-engines/watermark-stamp)
* [Metadata](/pdf-engines/metadata) — read/write metadata and bookmarks
* [Split](/pdf-engines/split)
* [Rotate](/pdf-engines/rotate)
* [Flatten](/pdf-engines/flatten)