Georgeshm wrote very sharp solution but forgot to write you can do it with Autocad then convert it..
If you have Autocad,
Way1: Open the file as Georgeshm told go layout.. right click, layout settings, change pen assigntment (at the top of right) to monochrome or grayscale...
Way2: Faster and easy open the file with Autocad. give "la" (Layer properties command) open the layers..
Select all click the attached colour box and change all to white. Then save as so don t lose original one..Convert it.. Issue is when you wanna do convert Pdf to Cad.. I couldn t find any safety way to do that. And I gave my Pdf to Autocad conversion job to company..
I hope you have Autocad and you can use one of method for your file.