# Documents and how they are indexed

> What happens between adding a file and the assistant being able to answer from it.

Source: https://welcomeai.dev/docs/documents
Category: Content
Updated: 2026-09-06

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A document is one piece of content: a file you uploaded, a page we crawled, an article a connector
sent, a Q&A pair you typed.

## What you can add

PDF, DOCX, PPTX, XLSX, CSV, Markdown, plain text and HTML. Plus anything a connector brings in, and
anything you push through the REST API.

A PDF that is a scan of paper has no text in it. We do not read images, so a scanned document arrives
empty. Run it through OCR first.

## What happens after you add one

1. **Extraction.** We pull the text out and keep the structure -- headings, lists, tables, and which
   page each passage came from, so a citation can say "page 7".
2. **Chunking.** The text is cut into passages of a few hundred words with a little overlap, so a
   sentence that straddles a boundary is not lost.
3. **Embedding.** Each chunk is turned into a list of numbers standing for its meaning. This is what
   makes "can I get my money back" find a paragraph about refunds.
4. **Indexed.** Now it can be answered from.

The whole thing takes seconds for a page and a minute or two for a long PDF. Status tells you where it
is, and a failure says why rather than sitting at "processing" forever.

## Re-indexing

Changing the chunk size, the overlap or the embedding model changes how every existing document was
processed, so those settings offer to re-index the knowledge base. It costs embedding tokens and a few
minutes; nothing is unavailable while it runs.

Editing the text of one document re-indexes only that one.

## Deleting

Deleting a document removes its chunks, its embeddings and the file we stored. It is immediate and it
is not recoverable, which is why the confirmation names the document.

Deleting the *source* a document came from is a different question, and the product asks it: you can
remove a connection and keep its documents, which is usually what you want -- they stop updating and
keep answering.

## Two things worth knowing

**More is not better.** A knowledge base with your ten clearest pages answers better than one with two
hundred pages of everything, because retrieval has fewer near-misses to choose between. Old versions of
a policy are worse than no policy.

**Titles matter more than you would think.** They are what a citation shows, and a document called
"Untitled" or "export-final-2.pdf" makes an answer look untrustworthy even when it is right.