Dumping the contains of the pdf results in a set of strange streams:
7 0 obj
<</Length 283>>
stream
2 w
120 650 m 140 650 l
140 645 m 140 625 l
120 620 m 140 620 l
120 615 m 120 595 l
120 590 m 140 590 l
S
endstream
endobj
It turns out to that it's a list of starting and ending points of lines, if we'd want to save that as postscript:
%%Page: 1 1
newpath
120 650 moveto
140 650 lineto
140 645 moveto
140 625 lineto
120 620 moveto
140 620 lineto
120 615 moveto
120 595 lineto
120 590 moveto
140 590 lineto
2 setlinewidth
stroke
fill
showpage
That way each stream is printed on a new page, we get:
Which decodes to:
SharifCTF{d1242d2d0969741dde7ed79c3c409c46}