Printing .pdf suddenly bad scale!

Hi,

Sorry for english. After a lot of work the last 2 days, my drawing isn't on good 100% scale when printing a .pdf. 
The scale is a little bit reduced, may be 96%.

I don't understand what happened so I'm sure the problem come from my file or some parameters I changed in this file. I'm sure of that because if I open a backup of this file (unfortunally 4 days ago) and I print a .pdf, the scale is good.

I'm sure also I didn't accidentally reduce my job, all dimensions and cotation are correct and the printers parameters didn't changed.

Thanks for your help, if somebody help me.

Patrick