SetDirectory["C:\\drorbn\\AcademicPensieve\\Classes\\16-1750-ShamelessMathematica"]

Make

Make::usage = "Make[targets, sources, Hold[action]] makes a target, or a list of targets, given sources, or a list of sources, in the style of the unix 'make' command.";
Make[target_String, sources_, action_Hold] := Make[Evaluate@{target}, sources, action];
Make[targets_, source_String, action__Hold] := Make[targets, Evaluate@{source}, action];
Make[targets_List, sources_List, action_Hold] := Module[{},
If[
(And @@ ((FileType[#] =!= None)& /@ sources)) &&
Or[
Or @@ ((FileType[#]===None)& /@ targets),
Min[AbsoluteTime[FileDate[#]]& /@ targets] < Max[AbsoluteTime[FileDate[#]]& /@ sources]
],
Print["Making ",targets, " ..."];
ReleaseHold[action]
]
];

Make["160208-OldKhoHo.png", "nb/160208-OldKhoHo.pdf", Hold[
DeleteFile[FileNames["temp-*.png"]];
Read["!convert -trim -scene 1 -density 300 -background white -alpha remove nb/160208-OldKhoHo.pdf temp.png"];
Read["!montage -geometry +0+0 -frame 0 -background white -tile 2x1 temp-*.png 160208-OldKhoHo.png"];
DeleteFile[FileNames["temp-*.png"]];
]]

{
  "TitleNotes" -> "<span style=\"color: red;\">
    Warning - the material here is my personal <a href=http://www.math.toronto.edu/~drorbn/classes/16-1750-ShamelessMathematica/>MAT 1750 \"Shameless Mathematica\"</a> notebook for 2016. No guarantee of any kind on anything that appears here.
    </span><p>",
"ImageComments" -> {}
}