The DeletePage function found in the Foxit SDK allows a page to be deleted from a PDF. When a page is deleted and the document saved, the file size of the output document (with fewer pages) is larger than the original.
This can be seen with the PDF sample app which ships with the SDK:
$ ./simple_sample/bin/rel_gcc/pdfpage_organization
...
Success: Use <rb> mode to open the file InsertPages.pdf and associate it with a stream.
Success: Create the file object.
Success: Open file successfully .
Success: Load PDF document successfully.
Success: Get page with index 1.
Success: Delete page with index 1.
Using extension implementation to open the file.
Success: Use <wb> mode to open the file SourcePage_delete.pdf and associate it with a stream.
Success: Create the file object.
Success: The PDF document save to SourcePage_delete.pdf.
Examining the output:
ll simple_sample/input_files/SourcePage.pdf -rw-r--r--@ 1 richard staff 92K Dec 17 2013 simple_sample/input_files/SourcePage.pdf
ll simple_sample/output_files/pdfpage_organization/SourcePage_delete.pdf -rw-r--r--@ 1 richard staff 96K Jun 23 10:22 simple_sample/output_files/pdfpage_organization/SourcePage_delete.pdf
SourcePage_delete.pdf does have one less page as expected, but is 4k bigger. I can get the same result deleting 99 pages from a 100 page document, i.e. the file size does not reflect the page count.
Based on the sample documents that you've provided and @MihaiIancu's comment you are saving an incremental PDF update which basically just appends new information to the end of your existing file.
According to the Foxit SDK site the function
FSPDF_Doc_StartSaveToFiletakes a flag for the third parameter which isFSPDF_SAVEFLAG_INCREMENTAL,FSPDF_SAVEFLAG_NOORIGINAL,FSPDF_SAVEFLAG_REMOVESECURITYorFSPDF_SAVEFLAG_OBJECTSTREAM. In your case I would think thatFSPDF_SAVEFLAG_NOORIGINALshould do what you're looking for. If you're not using this function directly there should still hopefully be a wrapper that takes one of these parameters.