Stering-PDf - Locally hosted web application that allows you to perform various operations on PDF files. See also PDFPea - Edit PDFs Online Securely and Free | Privacy-First PDF Editor
Dangerzone - Convert potentially dangerous documents into safe PDFs
ExifTool by Phil Harvey -Read, Write and Edit Meta Information!
QPDF - A Content-Preserving PDF Transformation System
Some of these above were found via
small script to cleanup pdfs in general (reducing their size as well), via.
pdftops -paper A4 -expand -level3 file.pdf
ps2pdf14 -dEmbedAllFonts=true \
-dUseFlateCompression=true \
-dOptimize=true \
-dProcessColorModel=/DeviceRGB \
-r72 \
-dDownsampleGrayImages=true \
-dGrayImageResolution=150 \
-dAutoFilterGrayImages=false \
-dGrayImageDownsampleType=/Bicubic \
-dDownsampleMonoImages=true \
-dMonoImageResolution=150 \
-dMonoImageDownsampleType=/Subsample \
-dDownsampleColorImages=true \
-dColorImageResolution=150 \
-dAutoFilterColorImages=false \
-dColorImageDownsampleType=/Bicubic \
-dPDFSETTINGS=/ebook \
-dNOSAFER \
-dALLOWPSTRANSPARENCY \
-dShowAnnots=false \
file.pdf file.pdf