Yes, it can be used to make pulp papier mache.

It is a harder paper than newspaper, so it takes a little more effort.

There are two kinds of shred, the long strips and the little cross-chopped pieces.  The little pieces seem easier to me, but I've used the strips -- I just chop them across the strips a bit more with scissors, but you probably wouldn't NEED to do that.

Put your shreds in a big pot of water and let it sit overnight.  Then put it on the stove and bring it up to a simmer.  This helps to break it down.

Then you can put the mush into a blender (Brits call it something else.. a liquifier?) with water and whirl it around.  You will have to use quite a bit of water when you do this, as blenders are made for use with watery things.  Too much drag on the blades and you'll burn out the motor.  Get one from a thrift shop, don't use your good one.  Start with a handful of pulp and a lot of water.

Pour the liquid mush into a wire sieve or a cone made from vinyl window screening and press out excess water to the degree that looks good to you.  Don't put the discarded water down the sink!  Putting it into the compost pile would be safer for your plumbing.

You can dry it thoroughly for future use, or go directly to adding your adhesive, dye, etc, and get to work on your project.

Pulp takes more time to dry than strips, so make sure it is dry before you start painting or sealing it.

Sue

it may be easier to dry for future use if you pick it out into small pieces and dry them on a screen.  You can also dry it in an oven on minimum heat. 

Salt is highly corrosive -- it will even destroy concrete eventually if you mix salty beach sand into the mix.

You can also use the office paper in strips, but you have to soak them well, first.  And the narrower the strips, the better.  If your strips are forming wrinkles, they're too wide or the pieces are too large.  Wrinkles mean sanding later.

Bleach and I don't get along very well, it makes me cough and it feels too slimy.

Sue

thank you all for your replies!