Design History file (DHF): Is a file that contains almost all the document from DID,DSD,DOD etc basically when you go back and look at this file you get to know all about the product development. It needs to be necessary that this documents needs to be updated all the time so that anytime even during product development you can refer a DHF. Since DHF is a document which contains so many documents within one document. We needs to make a checklist of all the documents under it and keep an eye on the project development throughout the development stage so that any changes that needs to be updated in the any related document would also be updated in the DHF.

For making sure that DHF is audit ready.
Company needs to make sure they have Mock audits on regular basis and before Mock audit QC should ensure that DIf,DOF have specified all specs in tolerance and if anything needs to be updated they are updated before the mock Inspection. If company has this mock inspection on regular basis rather than few just before inspection that could lead to consequences due to last minute changes and some changes might not be reflected on DHF which would be fatal.

So in order to make sure DHF is audit ready:
Make a checklist of all documnets required in DHF.
Have regular Mock Inspection.
Make QC have reqular inspection of any changes in DIF or DOF.
Make sure department notifies regulatory of any changes in Related documents.
Update DHF with any changes.