PDF form terms, defined.
Plain-language definitions for the words behind fillable PDFs and form automation.
Model Context Protocol (MCP)
The Model Context Protocol (MCP) is an open standard for connecting AI assistants such as Claude, ChatGPT, or Gemini to outside tools and data. A product exposes an MCP server; the assistant discovers the server's tools, asks the user to sign in when needed, and calls the tools on the user's behalf during a conversation.
Read the definition →MCP server
An MCP server is a program that exposes a set of tools to AI assistants using the Model Context Protocol. Each tool has a name, a description, an input schema, and hints about whether it reads or writes. Assistants connect to the server, list its tools, and call them during a conversation, with the user signing in first when the server requires it.
Read the definition →Fillable PDF
A fillable PDF is a PDF document that contains interactive form fields: text boxes, checkboxes, radio buttons, and signature areas that a person or program can complete without altering the underlying page.
Read the definition →Flat vs. fillable PDF
A flat PDF is a static page with no interactive form fields; you cannot type into it. A fillable PDF carries interactive fields layered on the page, so it can be completed on screen and read back as data.
Read the definition →Form field detection
Form field detection is the process of automatically locating where a document's input fields belong: text lines, checkboxes, radio options, and signature areas, and classifying each so interactive fields can be placed on the page.
Read the definition →PDF form
A PDF form is a PDF document designed to collect information: names, dates, choices, signatures. It may carry interactive fields that capture the values as data, or it may be a static page meant to be printed and completed by hand.
Read the definition →AcroForm
An AcroForm is the PDF specification's native format for interactive form fields: text boxes, checkboxes, radio buttons, dropdowns, and signature fields embedded in the document. A PDF with an AcroForm can be completed on screen and read back as data.
Read the definition →Form flattening
Form flattening converts a filled PDF's interactive fields into fixed page content: the values are painted onto the page and the editable fields are removed. The result looks identical but can no longer be changed or read back as form data.
Read the definition →Signature field
A signature field is an interactive PDF form field reserved for a signature: a specific region of the page that captures or holds a signer's mark, separate from ordinary text fields. It marks where a person is expected to sign.
Read the definition →OCR for forms
OCR (optical character recognition) reads the text in a scanned or image-based document and converts it from pixels into machine-readable characters. For a scanned PDF form, OCR recovers the labels and text that a plain image does not expose.
Read the definition →Checkbox and radio fields
Checkbox and radio fields are the interactive PDF form fields that capture choices. A checkbox toggles one option on or off independently; radio buttons form a group where selecting one clears the others, so exactly one choice is active.
Read the definition →Filling a PDF from data
Filling a PDF from data is the process of writing values into a fillable PDF's fields programmatically, from a database row, an API payload, or a document, instead of typing them by hand. It matches each value to the right field and sets it.
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