There are many different font types and then many different ways a font can be defined within a PDF so there is no sure way to update / trim a font without know all the parameters.

Here are some of the things that need to be accounted for

Encodings

CMaps

Differences

GIDToCID maps

ToUnicode (not so urgent)

The you need to determine the fonttype - Type1, Type3 etc..  Then you would need to extract the font descriptor and decode it to remove unused characters but make sure that you get the correct characters based on the encodings above.

We would need to see the PDF file to determine what was required to get it working correctly without making the text unreadable.

Andrew

Did you try this:

http://www.debenu.com/docs/pdf_library_reference/ReplaceFonts.php

 

already created pdf-files couldn't be compressed by QuickPDF on the fly.

You have to split the pdf into single pages, objects, ... and resample them to a new pdf using functions like CompressImages:

You should Keep in mind that Images have many Bytes and often there are jpg-images included which are already (as jpeg) compressed. So working on the images reducing the dpi will reduce much.

Defining/including font-properties and often used Images only once in the file can reduce, too.

 

Cheers, Ingo