Error in logs: kernel[0]: Validation failed, dataSuffix
These errors are reported by kernel and are caused by corruptive file compression in HFS+.

Suggestions:


Please run Disk Utility to Verify Disk for any file-system inconsistency (as well as Verify and Repair Disk Permissions),
If you're using any compression software tool, you may consider to upgrade it or remove it (e.g. Clusters),
Run Console and check 'Diagnostic and Usage Info -> User/System Diagnostic Reports' for any kernel or software crashes which could potentially cause that problems, 
Re-install completely the software which is failing (e.g. Pages),
Use Time Machine to recover the files from when it was working, 
This could be some hardware issue, please run S.M.A.R.T. tests for your HDD to find any issues or bad sectors,
This you're using SSD, it could have been heavily used (as it has quite short life span in comparision to HDD) or you could be using some bad quality product,
If anything won't help, you may try to make an appointment with Genius Bar.