diff --git a/document.lua b/document.lua
new file mode 100644
index 000000000..546cf82d8
--- /dev/null
+++ b/document.lua
@@ -0,0 +1,253 @@
+--[[
+This is a registry for document providers
+]]--
+DocumentRegistry = {
+	providers = { }
+}
+
+function DocumentRegistry:addProvider(extension, mimetype, provider)
+	table.insert(self.providers, { extension = extension, mimetype = mimetype, provider = provider })
+end
+
+function DocumentRegistry:getProvider(file)
+	-- TODO: some implementation based on mime types?
+	local extension = string.lower(string.match(file, ".+%.([^.]+)"))
+	for _, provider in ipairs(self.providers) do
+		if extension == provider.extension then
+			return provider.provider:new{file = file}
+		end
+	end
+end
+
+--[[
+This is an abstract interface to a document
+]]--
+Document = {
+	-- file name
+	file = nil,
+
+	info = {
+		-- whether the document is pageable
+		has_pages = false,
+		-- whether words can be provided
+		has_words = false,
+		-- whether hyperlinks can be provided
+		has_hyperlinks = false,
+		-- whether (native to format) annotations can be provided
+		has_annotations = false,
+
+		-- whether pages can be rotated
+		is_rotatable = false,
+
+		number_of_pages = 0,
+		-- if not pageable, length of the document in pixels
+		length = 0,
+
+		-- other metadata
+		title = "",
+		author = "",
+		date = ""
+	},
+
+	-- flag to show whether the document was opened successfully
+	is_open = false,
+	error_message = nil,
+
+	-- flag to show that the document needs to be unlocked by a password
+	is_locked = false,
+}
+
+function Document:new(o)
+	local o = o or {}
+	setmetatable(o, self)
+	self.__index = self
+	if o.init then o:init() end
+	return o
+end
+
+-- this might be overridden by a document implementation
+function Document:unlock(password)
+	-- return true instead when the password provided unlocked the document
+	return false
+end
+
+-- this might be overridden by a document implementation
+function Document:close()
+end
+
+-- this might be overridden by a document implementation
+function Document:getNativePageDimensions(pageno)
+	return Geom:new{w=0, h=0}
+end
+
+-- calculates page dimensions
+function Document:getPageDimensions(pageno, zoom, rotation)
+	local native_dimen = Geom:copy(self:getNativePageDimensions(pageno))
+	if rotation == 90 or rotation == 270 then
+		-- switch orientation
+		native_dimen.w, native_dimen.h = native_dimen.h, native_dimen.w
+	end
+	native_dimen:scaleBy(zoom)
+	debug("dimen for pageno", pageno, "zoom", zoom, "rotation", rotation, "is", native_dimen)
+	return native_dimen
+end
+
+
+
+require "cache"
+require "geometry"
+
+
+PdfDocument = Document:new{
+	_document = false,
+	-- muPDF manages its own additional cache
+	mupdf_cache_size = 5 * 1024 * 1024,
+	dc_null = DrawContext.new()
+}
+
+function PdfDocument:init()
+	local ok
+	ok, self._document = pcall(pdf.openDocument, self.file, self.mupdf_cache_size)
+	if not ok then
+		self.error_message = self.doc -- will contain error message
+		return
+	end
+	self.is_open = true
+	self.info.has_pages = true
+	if self._document:needsPassword() then
+		self.is_locked = true
+	else
+		self:_readMetadata()
+	end
+end
+
+function PdfDocument:unlock(password)
+	if not self._document:authenticatePassword(password) then
+		self._document:close()
+		return false, "wrong password"
+	end
+	self.is_locked = false
+	return self:_readMetadata()
+end
+
+function PdfDocument:_readMetadata()
+	self.info.number_of_pages = self._document:getPages()
+	return true
+end
+
+function PdfDocument:close()
+	if self.is_open then
+		self.is_open = false
+		self._document:close()
+	end
+end
+
+function PdfDocument:getNativePageDimensions(pageno)
+	local hash = "pgdim|"..self.file.."|"..pageno
+	local cached = Cache:check(hash)
+	if cached then
+		return cached[1]
+	end
+	local page = self._document:openPage(pageno)
+	local page_size_w, page_size_h = page:getSize(self.dc_null)
+	local page_size = Geom:new{ w = page_size_w, h = page_size_h }
+	Cache:insert(hash, CacheItem:new{ page_size })
+	page:close()
+	return page_size
+end
+
+function PdfDocument:getUsedBBox(pageno)
+	local hash = "pgubbox|"..self.file.."|"..pageno
+	local cached = Cache:check(hash)
+	if cached then
+		return cached.data
+	end
+	local page = self._document:openPage(pageno)
+	local used = {}
+	used.x, used.y, used.w, used.h = page:getUsedBBox()
+	Cache:insert(hash, CacheItem:new{ used })
+	page:close()
+	return used
+end
+
+function PdfDocument:getPageText(pageno)
+	-- is this worth caching? not done yet.
+	local page = self._document:openPage(pageno)
+	local text = page:getPageText()
+	page:close()
+	return text
+end
+
+function PdfDocument:renderPage(pageno, rect, zoom, rotation)
+	local hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation
+	local page_size = self:getPageDimensions(pageno, zoom, rotation)
+	-- this will be the size we actually render
+	local size = page_size
+	-- we prefer to render the full page, if it fits into cache
+	if not Cache:willAccept(size.w * size.h / 2) then
+		-- whole page won't fit into cache
+		debug("rendering only part of the page")
+		-- TODO: figure out how to better segment the page
+		if not rect then
+			debug("aborting, since we do not have a specification for that part")
+			-- required part not given, so abort
+			return
+		end
+		-- only render required part
+		hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..tostring(rect)
+		size = rect
+	end
+
+	-- prepare cache item with contained blitbuffer	
+	local tile = CacheItem:new{
+		size = size.w * size.h / 2 + 64, -- estimation
+		excerpt = size,
+		pageno = pageno,
+		bb = Blitbuffer.new(size.w, size.h)
+	}
+
+	-- create a draw context
+	local dc = DrawContext.new()
+
+	dc:setRotate(rotation)
+	-- correction of rotation
+	if rotation == 90 then
+		dc:setOffset(page_size.w, 0)
+	elseif rotation == 180 then
+		dc:setOffset(page_size.w, page_size.h)
+	elseif rotation == 270 then
+		dc:setOffset(0, page_size.h)
+	end
+	dc:setZoom(zoom)
+
+	-- render
+	local page = self._document:openPage(pageno)
+	page:draw(dc, tile.bb, size.x, size.y)
+	page:close()
+	Cache:insert(hash, tile)
+
+	return tile
+end
+
+-- a hint for the cache engine to paint a full page to the cache
+-- TODO: this should trigger a background operation
+function PdfDocument:hintPage(pageno, zoom, rotation)
+	self:renderPage(pageno, nil, zoom, rotation)
+end
+
+function PdfDocument:drawPage(target, x, y, rect, pageno, zoom, rotation)
+	local hash_full_page = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation
+	local hash_excerpt = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..tostring(rect)
+	local tile = Cache:check(hash_full_page)
+	if not tile then
+		tile = Cache:check(hash_excerpt)
+		if not tile then
+			debug("rendering")
+			tile = self:renderPage(pageno, rect, zoom, rotation)
+		end
+	end
+	debug("now painting", tile)
+	target:blitFrom(tile.bb, x, y, rect.x - tile.excerpt.x, rect.y - tile.excerpt.y, rect.w, rect.h)
+end
+
+DocumentRegistry:addProvider("pdf", "application/pdf", PdfDocument)