I am embedding links to an UR in my documents. Although it is used in XML-documents, you might be able to use the gist of this code that generates a clickable link. Perhaps you find it useful. 

dr. Hans van der Meer

% Return the code when clicking the link.
\def\URIReturnCode#1{\ctxlua{tex.print(hvdm.urireturncode("#1"))}}

— Some Lua code needed:
-- Check URI

	socket.http.TIMEOUT = 5					-- set URI timeout in seconds
	hvdm.urireturncode = function (theuri)
		-- Differentiate between file and http protocols.
		local first,last = string.find(theuri, "file://")
		if first == nil then
			-- We have http to search for.
			local content, status, authinfo = socket.http.request{
				method = "HEAD",
				url = theuri,
				}
			return type(status) == "number" and status or "failure"
		else
			-- We must ascertain the existence of the file.
			local thefile = io.open(string.sub(theuri, last+1, -1), "r")
			if thefile then
				io.close(thefile)
				return "200"
			else
				return "404"
			end
		end
	end

% ..... Place an url link .....................................................

% BEWARE: spaces in file names must be %20 in the link !!!

% This global definition of the URLbase cannot be missed.
\def\THEURLBASE{http://}

% Signal the occurence of timeout on URI search.
\newif\ifURItimeout

\startxmlsetups xmlcommon:urlbase
	\edef\THEURLBASE{\xmlstrippednolines{#1}{.}}

	% Reset the URI timeout for new URLbase.
	\global\URItimeoutfalse
\stopxmlsetups

\startxmlsetups xmlcommon:url

	% Define the full uri.
	\edef\theurl{\THEURLBASE\xmlatt{#1}{link}}

	 % File suffix should be one of the list.
	\doifelse{\FileSuffixList{\xmlatt{#1}{link}}
			{pdf,jpg,jpeg,html,png,tif,tiff}}{\empty}
		{\def\suffix{.impossible}}% no suffix from the list here
		{\def\suffix{\empty}}% one of the list is present

	% First try link as given, beware of unreachable site.
	\ifURItimeout
		% For previously timeout on this site.
	\else
		\edef\returncode{\URIReturnCode{\theurl}}
		\doif{\returncode}{failure}
		{
			\global\URItimeouttrue
			\errorcall{#1}{url access fails for \THEURLBASE\xmlatt{#1}{link}}
		}
	\fi

	% On URI timeout there is no hope to find the file.
	\ifURItimeout
	\else
		% When there is no suffix from the list, try several.
		\doifnot{\suffix}{\empty}
		{
			\scratchcounter=200\relax
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.pdf}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.jpg}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.jpeg}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.html}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.png}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.tiff}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
			\ifnum\returncode=\scratchcounter\else
				\def\suffix{.tif}
				\edef\returncode{\URIReturnCode{\theurl\suffix}}
			\fi
		}

		% Give up if returncode other then 200.
		\ifnum\returncode=200\relax
			% Page number might be added.
			\doifelse{\xmlatt{#1}{page}}{\empty}
				{\let\thep\empty}
				{\edef\thep{\letterhash page=\xmlatt{#1}{page}}}

			% Place the link, ref-attribute prevales in the presentation.
			\doifelse{\xmlatt{#1}{ref}}{\empty}
				{\edef\temp{\xmlatt{#1}{link}}}
				{\edef\temp{\xmlatt{#1}{ref}}}
			\goto
				{\FirstLastCharacters{\temp}{\xmlatt{#1}{maxsize}}}
				[url(\theurl\suffix\thep)]
		\else
			\errorcall{#1}
				{\THEURLBASE\xmlatt{#1}{link} not found (\returncode)}
		\fi

	\fi	% end of URItimeout
\stopxmlsetups


> On 8 Oct 2018, at 00:39, Hans Hagen <j.hagen@xs4all.nl> wrote:
> 
> On 10/7/2018 8:41 PM, Pablo Rodriguez wrote:
>> On 10/7/18 8:33 PM, Hans Hagen wrote:
>>> On 10/7/2018 8:19 PM, Pablo Rodriguez wrote:
>>>> [...]
>>>> Is there a way to hyperlink to an attached document? I mean, no matter
>>>> whether it has been generated by ConTeXt or not.
>>>> i have no clue what you mean
>> Is there a way to link to a page or a destination (such as in
>> https://www.adobe.com/content/dam/acom/en/devnet/pdf/PDF32000_2008.pdf#page=500
>> or
>> https://www.adobe.com/content/dam/acom/en/devnet/pdf/PDF32000_2008.pdf#nameddest=G12.2456615)
>> to a document that is attached (using \attachment) in ConTeXt?
>> I hope it is clear now,
> it points to the media mess .. which relates to either or not obsolete stuff (flash related)
> 
> anyway, i don't know as i never embed pdf docs and if i would i'd have no reason to refer to them (it probably depends on a viewer extracting the attachment, caching it and then providing access: it makes no sense to waste time on features that are not supported or maybe only by acrobat unless it's a well paid projects in which case throw away code is a bit less waste of time because it brings foon on the table)
> 
> Hans
> 
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