suddenly unable to save psd as a pdf Error msg 'unable to save..because of a prorgram error

Suddenly ,out of the blue , unable to save psd docs as pdfs.

Was able though this morning top save as jpeg

Using macbook pro 15" 2017

2.9 GHz Quad-Core Intel Core i7

Radeon Pro 560 4 GB

Intel HD Graphics 630 1536 MB

using venture 13.6.7

Interestingly, mac does auto updates but when i went to check under help ( within photoshop for updates ) it was greyed out. Doe sthis mean its up to date or unavaialbale for some reason?

I've force quitted phtoshop and restarted computer a couple of times 

Can anyone help? Its such a basic and necessary function