Remove multiple text watermarks from a PDF file. Requires xxd and qpdf to work correctly.

remove-pdf-watermark.sh

#!/bin/bash

# Remove multiple text watermarks from a PDF file.  Requires xxd and qpdf to work correctly.
#
# Usage:
#
#   remove-pdf-watermark.sh "Your Input File.pdf" "Your Output File.pdf" [WATERMARK1] [WATERMARK2] [WATERMARK3] [...]
#
# For Example:
#
#   remove-pdf-watermark.sh "Your Input File.pdf" "Your Output File.pdf" "Watermark 1" "Watermark 2"
#

# This is a more general (lesser dependencies, more functionality, but slower) version of
# https://gist.github.com/elfsternberg/a96883018d783cbbad7b454ecd0a7ffe


INPUT_FILENAME=$1
OUTPUT_FILENAME=$2

echo "Processing: $INPUT_FILENAME"

UNCOMPRESSED=`mktemp -t 'uncompressed'`
UNCOMPRESSED_HEX=`mktemp -t 'uncompressed-hex'`
UNMARKED_PRE=`mktemp -t 'unmarked-pre'`

qpdf --stream-data=uncompress --decode-level=all "$INPUT_FILENAME" $UNCOMPRESSED
echo " - Decompressing to: $UNCOMPRESSED"
xxd -ps -c 0 $UNCOMPRESSED > $UNCOMPRESSED_HEX
echo " - Hex dumping to: $UNCOMPRESSED_HEX"

rm $UNCOMPRESSED

for ARG in "$@"; do
    COUNT=$((COUNT+1))
    if [[ $COUNT -gt 2 ]]
    then
        WATERMARK=$ARG
        echo " - Processing Watermark: \"$WATERMARK\""
        WATERMARKLEN=${#WATERMARK}
        WATERMARK_HEX=$(echo -n $WATERMARK | xxd -p -c 0)
        BLANKS=$(printf %${WATERMARKLEN}s)
        BLANKS_HEX=$(echo -n "$BLANKS" | xxd -p -c 0)

        NUM_OCCURENCES_=$(grep -o $WATERMARK_HEX $UNCOMPRESSED_HEX | wc -l)
        NUM_OCCURENCES=$((0+$NUM_OCCURENCES_))
        echo "    * Number of occurences: $NUM_OCCURENCES"

        if [[ $NUM_OCCURENCES -gt 0 ]]
        then
            echo "    * Replacing with $WATERMARKLEN blanks..."
            sed -i -e "s/$WATERMARK_HEX/$BLANKS_HEX/g" $UNCOMPRESSED_HEX
            echo "    * Replacement done."
            NUM_OCCURENCES_=$(grep -o $WATERMARK_HEX $UNCOMPRESSED_HEX | wc -l)
            NUM_OCCURENCES=$((0+$NUM_OCCURENCES_))
            echo "    * Final number of occurences: $NUM_OCCURENCES"
        fi
    fi
done

xxd -r -p -c 0 $UNCOMPRESSED_HEX $UNMARKED_PRE

rm $UNCOMPRESSED_HEX

echo " - Reverting from hex dump to: $UNMARKED_PRE"

qpdf --stream-data=compress $UNMARKED_PRE "$OUTPUT_FILENAME"

rm $UNMARKED_PRE

echo " - Output written to: $OUTPUT_FILENAME"
echo
echo


# NO WARRANTY
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.