Here's a start: Tag is a command line tool to manipulate tags in Mavericks.
ExifTool is a command line tool for writing metadata into images.
So you need to do something like this to glue them together in a command line function:
function tags2metadata(){
tags=$(tag -N "$1");
exiftool -Keywords="${tags//,/, }" "$1";
tag --add "$tags" "$1";
}
tags=$(tag -N "$1");
harvests the tags as a comma separated list (the -N option is to avoid it displaying the file name in its output), eg good,bad,ugly
exiftool -Keywords="${tags//,/, }" "$1";
adds the tags to the "Keyword" metadata field in the pdf metadata (the expression ${tags//,/, }
replaces every comma in $tags
with comma+space, so that they become separate keywords).
Now exiftool creates a new file with the name of the original file and renames the original; eg. foo.pdf is renamed to foo.pdf_original and a new file foo.pdf is created with the modified metadata. You can change this by adding -overwrite_original
to the exiftool command like this:
exiftool -overwrite_original -Keywords="${tags//,/, }" "$1";
but I chose to just re-write the mavericks Finder tags to the new file using tag --add "$tags" "$1";
($1 in a function stands for the input it is given).
So to use it, you could then open a terminal, type in the script above, cd
to the directory with your pdfs in it and do:
for i in *.pdf
do tags2metadata "$i"
done
If you open the new file and check for keywords, you should find all your Finder tags in there.
To install tags and exiftool I recommend Homebrew. Once you've installed it you just need to type brew install exiftool tag
and it will do the necessary magic for you.
Please test this on files that you don't mind screwing up before you let it loose on your good stuff.