Hey guys, I am beginner in Inquisit and I would appreciate your help.
So I'm conducting an experiment which involve text stimuli that participants would have to read. I'm thinking about 3 full pages of text. I want it to be system paced i.e. their reading times should be limited with no option to turn to previous page. 
Is it possible to insert some sort of timer that will be showing remaining time across all of that three pages? 
Any help is appreciated..

Yes, you can run three trials in a <block>; set the reading time you want to allow for each page (that is: trial) via the <trial>'s /trialduration. Display a <clock> element displaying a countdown of the total time allowed via the <block>'s /bgstim. In short:

<defaults>
/ screencolor = black
</defaults>

<block pageblock>
/ bgstim = (countdown)
/ trials = [1-3 = pagetrial]
</block>

<trial pagetrial>
/ stimulusframes = [1=textpage]
/ validresponse = (0)
/ trialduration = 5000
</trial>

<text textpage>
/ items = textpages
/ select = sequence
/ size = (80%, 80%)
/ txbgcolor = white
/ erase = false
/ vjustify = top
/ hjustify = left
</text>

<item textpages>
/ 1 = "Page 1..."
/ 2 = "Page 2..."
/ 3 = "Page 3..."
</item>

<clock countdown>
/ mode = timer
/ format = "ss"
/ timeout = 15000
/ position = (90%, 5%)
</clock>