Answering my own comment (well, partially)…
Where there are “styles” applied to paragraphs, the “Autocorrect > Apply” solution will not work. However, it is possible to use regex search-replace to speed up this process enormously. The instructions below are based on a very helpful discussion on the OpenOffice forum (do read through to the end, if it’s of interest).
Double quotes
Hit CTRL-H to bring up the search/replace dialog; use the “More Options” drop-down, and select [x] Regular expressions. Paste in the following values:
First, Search for:
"(\<|[\[\(])
Replace with:
“$1
Click “Replace All”.
Then, Search for:
(\>|[,.;!?\]\)])"
Replace with:
$1”
Click “Replace All”. Now do a simple search for " (straight double-quote) to see if any have been missed. There shouldn’t be many!
Single quotes
Much simpler: Search for [space]'
and replace with [space]‘
for opener, then simply change all the rest of the '
marks to closer ’
and that should do it. There might be cases of ('
or ['
which need to be catered for (my doc didn’t have any), but the technique used for the double quotes will take care of those.
There must be a way of putting this all into a macro, but I haven’t thought about that yet. So – if preserving paragraph styles is important (it was to me in a 44-page imported and heavily styled document!), then this regex approach will get the job done very, very quickly.