@spec extract_pages(PDFium.source(), [non_neg_integer()]) ::
  {:ok, binary()} | {:error, atom()}

Writes the given pages, counted from zero and in the order asked for, as a document of their own.

{:ok, binary} = PDFium.Toolbox.extract_pages("contract.pdf", [0, 2])

@spec flatten(PDFium.source(), :display | :print, PDFium.security()) ::
  {:ok, binary()} | {:error, atom()}

Draws every annotation into the page it sits on and drops it.

{:ok, binary} = PDFium.Toolbox.flatten("contract.pdf")
{:ok, binary} = PDFium.Toolbox.flatten("contract.pdf", :print, :remove)

@spec merge([PDFium.source()]) :: {:ok, binary()} | {:error, atom()}

Writes the documents as one, in the order given.

{:ok, binary} = PDFium.Toolbox.merge(["contract.pdf", {:bytes, attachment}])

@spec overlay(PDFium.source(), PDFium.source()) :: {:ok, binary()} | {:error, atom()}

Draws each page of overlay_source over the page of source in the same place, scaled to fit and centred. The two must have the same number of pages.

{:ok, binary} = PDFium.Toolbox.overlay("contract.pdf", {:bytes, header_and_footer})

@spec render_pages!(PDFium.source(), pos_integer()) :: Enumerable.t()

Renders every page of source at dpi, one at a time as the stream is read, each as {pixels, width, height} in RGBA. Raises when the document cannot be opened.

PDFium.Toolbox.render_pages!("contract.pdf", 150) |> Enum.map(&to_png/1)

@spec stamp(
  PDFium.source(),
  [{PDFium.source(), non_neg_integer()}],
  PDFium.security()
) ::
  {:ok, binary()} | {:error, atom()}

Draws overlays over pages of source, each scaled to fit and centred.

{:ok, binary} = PDFium.Toolbox.stamp("contract.pdf", [{"signature.pdf", 2}])

A placement is {overlay, page_index}, pages counted from zero. An overlay is drawn by its first page, and placements on one page stack in the order given.