# useDocumentSaving

Source: https://sdk.pdf.net/docs/v1/reference/useDocumentSaving



Builds the final PDF from the loaded document and the changes recorded during the session (see [Building a PDF application](https://sdk.pdf.net/docs/v1/guides/building-a-pdf-application) for how changes are tracked).

```ts
const { prepareDocument, downloadDocument } = useDocumentSaving()
```

Both functions are asynchronous, accept the same options, and throw `DocumentNotLoadedError` when no document is loaded:

* `prepareDocument(options?)` resolves with the document bytes (`Uint8Array`) for your own handling, such as uploading to a server.
* `downloadDocument(options?)` builds the same bytes and saves them on the user's device as a file.

## Options [#options]

| Option                      | Default   | What it does                                                                                                                                                                                                                                                                                                         |
| --------------------------- | --------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `pageIds`                   | all pages | The pages to save, as an iterable of page ids, in the order they appear in the saved PDF: `[thirdPageId, firstPageId]` saves the third page first. The other pages are left out. Without it, the saved PDF has the current pages in their current order.                                                             |
| `returnOriginalIfUnchanged` | `true`    | When the saved document has no changes, the original buffer passed to `loadPdf` is returned directly, with no copy. Set to `false` when you intend to transfer or mutate the returned buffer (e.g. pass it to a worker), otherwise the loaded document's `ArrayBuffer` gets detached and later document reads throw. |

`pageIds` must list at least one page, and each page at most once, or the call throws `InvalidInputError`; so does an id of a page that doesn't exist or is deleted. To save a page twice, duplicate it first with [usePageDuplicate](https://sdk.pdf.net/docs/v1/reference/usePageDuplicate). A `Set` keeps the ids unique and in insertion order.

## Example [#example]

```tsx
import { useDocumentSaving } from '@sdk-pdf/react'

function useUploadDocument() {
  const { prepareDocument } = useDocumentSaving()

  return async () => {
    // The buffer is transferred to fetch, so don't hand out the original.
    const buffer = await prepareDocument({ returnOriginalIfUnchanged: false })
    await fetch('/api/documents', { method: 'PUT', body: buffer as BodyInit })
  }
}

function useDownloadPages() {
  const { downloadDocument } = useDocumentSaving()

  // Saves only the given pages, such as the ones the user picked in a page list.
  return (pageIds: Set<string>) => downloadDocument({ pageIds })
}
```

To save only when the document has changed since the last save, compare revisions with [useDocumentRevisionGetter](https://sdk.pdf.net/docs/v1/reference/useDocumentRevisionGetter).