A set of character to string substitutions used for translating
typographic characters like ligatures into more normal text.
PDF text often includes typographic characters that are uncommon
in normal text. For example these may include ligatures such as
'ff' or 'fl'. They may include different types of dash such as
n-dash and m-dash. They may include curly/smart single and double
quote characters. For the purposes of text extraction and searching
it is generally desirable to replace these characters with their
more common equivalents.
The default settings for this operation include the
substitutions of the types of characters detailed above. The
default settings are liable to change so if it is important that
your settings remain constant between different versions of ABCpdf
you should assign your own values.