To include a file with no text (e.g. a PDF containing only images or for
which the conversion to HTML failed) you'll need to hack
gsdl/perllib/plugins/ConvertToPlug.pm. In the read() function of this
module you'll see a block of code like the following:

&BasPlug::read_file($self, $conv_filename, $encoding, $language, $text);
if (!length ($text)) {
my $plugin_name = ref ($self);
print $outhandle "$plugin_name: ERROR: $file contains no text " if
$self->{'verbosity'};
return 0;
}

This forces all plugins derived from ConvertToPlug (i.e. PDFPlug,
WordPlug etc.) to ignore a file if no text could be extracted from it.
By commenting out or deleting the line reading "return 0;" you should be
able to get it to continue and include the file.

We should probably add a new plugin option to allow this as it's
preferable to include the file in many cases (even though text wasn't
extracted so it's not full-text searchable).

regards,
Stefan.