beta

Watermark PDF documents

🤖/document/watermark adds personalized text watermarks to every page of a PDF.

{
  "robot": "/document/watermark",
  "use": ":original",
  "text": "Licensed to ${fields.name}",
  "position": "top-left",
  "margin": 0,
  "rotation": 0,
  "x_offset": 72,
  "y_offset": 144
}

Usage example

{
  "steps": {
    "watermarked": {
      "robot": "/document/watermark",
      "text": "${fields.watermark}",
      "use": ":original"
    }
  }
}

Parameters

• interpolate

  boolean | Record<string, boolean>

  Controls whether Assembly Variables are interpolated for individual instruction fields.

  By default, most Robot instruction fields interpolate Assembly Variables. Set this to false to treat every instruction field as literal text, or set an individual field path to false to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to true or set that field path to true to opt back into interpolation.

  Use field names such as path, or dotted paths such as ffmpeg.vf for nested objects.

• output_meta

  Record<string, boolean> | boolean | Array<string>

  Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.

  For images, you can add "has_transparency": true in this object to extract if the image contains transparent parts and "dominant_colors": true to extract an array of hexadecimal color codes from the image.

  For images, you can also add "blurhash": true to extract a BlurHash⁠ string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads.

  For images, "thumbhash": true instead extracts a base64-encoded ThumbHash⁠ into meta.thumbhash, together with meta.has_alpha (whether an alpha channel exists, even when fully opaque). It describes EXIF-oriented pixels and uses the first frame of animated images. Extraction is best-effort: images above 40 megapixels, unsupported formats, or a failed/bounded decode produce no placeholder. Successful extraction adds a metadata charge equivalent to 20% of that file's bytes. No ThumbHash surcharge applies when disabled or when no hash is produced.

  Set this option on the Step producing the image, such as /upload/handle for uploaded originals or /image/resize for processed outputs. Setting it only on /transloadit/store does not request extraction: storage preserves the producer's metadata. Transloadit Storage persists a generated hash with its immutable version and returns it in stored results and native asset reads. Direct S3 uploads do not generate placeholders. A placeholder contains image information, so protect it with the same access controls as the full image.

  For videos, you can add the "colorspace": true parameter to extract the colorspace of the output video.

  For videos, you can also add "interlaced": true to detect whether the video is interlaced. This combines the cheap ffprobe field_order flag with a bounded idet sampling pass over the first frames of the source, exposing interlaced, field_order, and a diagnostic interlace_detection object under file.meta. This is computationally expensive and billed accordingly.

  For audio, you can add "mean_volume": true to get a single value representing the mean average volume of the audio file.

  You can also set this to false to skip metadata extraction and speed up transcoding.

• user_meta

  Record<string, any>(default: {})

  Adds custom JSON metadata to each emitted file without changing its contents. Nested objects and arrays are supported.

  Inheritance depends on the Robot. Values merge with existing user_meta on the output file; the current Step replaces matching top-level keys. Assign required keys explicitly when a Robot creates fresh outputs.

  In processing Steps, ${file.*} refers to the first input and ${result.*} to the emitted file. Values are evaluated per output after the Robot runs, before subsequent metadata extraction and temporary storage. On :original, values are evaluated per upload before metadata extraction.

  Downstream Steps read ${file.user_meta.key}. See Custom metadata for a complete example and inheritance rules.

• result

  boolean(default: false)

  Whether the results of this Step should be present in the Assembly Status JSON

• queue

  batch

  Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times

• force_accept

  boolean(default: false)

  Force a Robot to accept a file type it would have ignored.

  By default, Robots ignore files they are not familiar with. 🤖/video/encode, for example, will happily ignore input images.

  With the force_accept parameter set to true, you can force Robots to accept all files thrown at them. This will typically lead to errors and should only be used for debugging or combatting edge cases.

• ignore_errors

  boolean | Array<meta | execute>(default: [])

  Ignore errors during specific phases of processing.

  Setting this to ["meta"] will cause the Robot to ignore errors during metadata extraction.

  Setting this to ["execute"] will cause the Robot to ignore errors during the main execution phase.

  Setting this to true is equivalent to ["meta", "execute"] and will ignore errors in both phases.

• use

  string | Array<string> | Array<object> | object

  Specifies which Step(s) to use as input.

  • You can pick any names for Steps except ":original" (reserved for user uploads handled by Transloadit)
  • You can provide several Steps as input with arrays:

    {
      "use": [
        ":original",
        "encoded",
        "resized"
      ]
    }
    

  • You can also tag input Steps with as to pass semantic intent to robots:

    {
      "use": [
        {
          "name": ":original",
          "as": "image"
        },
        {
          "name": ":original",
          "as": "mask"
        }
      ]
    }
    

  Tip

  That's likely all you need to know about use, but you can view Advanced use cases.

• text — required

  string

  The text to place on every page. Use Assembly Variables such as ${fields.watermark} to personalize each request. Newlines create multiple lines of text. Characters must be available in the selected font; unsupported characters return an error.

• font

  DejaVu Sans | DejaVu Serif | DejaVu Sans Mono(default: "DejaVu Sans")

  The embedded font used for the watermark.

• font_size

  string | number(default: 36)

  The maximum font size in PDF points. Text is reduced to fit within the page margins.

• color

  string(default: "#808080")

  The watermark color as a six-digit hexadecimal RGB value.

• opacity

  string | number(default: 0.25)

  The watermark opacity, from 0 (fully transparent) to 1 (fully opaque).

• position

  bottom | bottom-left | bottom-right | center | left | right | top | 2 more ↓(default: "center")

  The position within the visible page, accounting for page rotation and cropping.

• x_offset

  string | number(default: 0)

  Horizontal offset from position, in PDF points (72 points = 1 inch). Positive values move right, except for right-aligned positions, where they move left. Negative values reverse that direction. Offsets follow the visible page axes, independent of the text rotation.

• y_offset

  string | number(default: 0)

  Vertical offset from position, in PDF points (72 points = 1 inch). Positive values move down, except for bottom-aligned positions, where they move up. Negative values reverse that direction. Offsets follow the visible page axes, independent of the text rotation.

• rotation

  string | number(default: 45)

  The counterclockwise rotation of the text in degrees, relative to the visible page.

• margin

  string | number(default: 24)

  The inset from the visible page edges, in PDF points, used to position and fit the watermark before applying x_offset and y_offset.