Add more PDF tips

how_to

@@ -220,6 +220,10 @@ PDF :
             # range can be <start>-<end>, more info at pdftk --help
         Uncompress pdf file content :
             pdftk input.pdf output output.pdf uncompress
+    Extract text from pdf (poppler):
+        pdftotext in.pdf out.txt
+    Extract images from pdf (poppler):
+        pdfimages <in.pdf> <imgs-prefix>
     Add images and other files in a single pdf:
         convert [jpg|png|txt|pdf|...] output.pdf
         # Might need to tweak /etc/ImageMagick-7/policy.xml
@@ -233,6 +237,19 @@ PDF :
             xournal
             libreoffice Draw
             inkscape
+        Batch mode with pdftk:
+            # http://www.myown1.com/linux/pdf_formfill.shtml
+            Finding the fields:
+                # pdftk needs java-commons-lang
+                pdftk form.pdf dump_data_fields_utf8 > fields.flds
+            Generating fdf file with values:
+                # https://github.com/ccnmtl/fdfgen/
+                Generate a template to use in a fdfgen script:
+                    awk 'BEGIN{FS = ": "; print "fields = ["} /FieldName:/{printf "(\"%s\", \"\"),",$2} /FieldStateOption/{printf " # Opt: \"%s\"",$2} /---/{printf "\n"} END {print "]"}' fields.flds > fields.py
+                # http://home.myfairpoint.net/vzenxj75/downloads/fdf_gen_20080304.tgz (brittle as hell)
+                fdf_gen fields.flds values.txt fields.fdf
+            Filling the form:
+                pdftk form.pdf fill_form fields.fdf output filled_form.pdf
 
 Fill dynamic XFA forms on linux:
     Run Acrobat Reader DC 2019 on wine: