[Foxit PDF SDK] How to combine PDF files? – Help Center | Foxit Software

There are several methods to combine PDF files by using Foxit PDF SDK：

Import pages from other PDF file to the target PDF file. (since v6.x)
Extract pages from PDF file and then insert extracted pages to target PDF file. (since v7.1)
Use class Combination. (since v7.4)

1. Import pages from other PDF file to the target PDF file.

Applicable version	v6.x or later.
Related APIs	foxit::pdf::PDFDoc::StartImportPages or foxit::pdf::PDFDoc::StartImportPagesFromFilePath
Import page flags
Sample demo	Please refer to simple demo "page_organization" in Foxit PDF SDK package.
Note	In one call to API StartImportPages() or StartImportPagesFromFilePath(), it's only possible to deal with 2 PDF files. (Impossible to combine several PDF files just in one time) Except layer, it's impossible to specify whether other information or which kind of object(s) in PDF page or PDF document should be imported to target PDF or not.

Applicable version	v7.1 or later.
Related APIs	foxit::pdf::PDFDoc::StartExtractPages and foxit::pdf::PDFDoc::InsertDocument
Extract page flags
Insert document options
Sample demo	Please refer to simple demo "page_organization" in Foxit PDF SDK package.
Note	In one call to API StartExtractPages(), it's only possible to extract pages from 1 PDF file. In one call to InsertDocument(), it's only possible to insert pages from 1 PDF file to another PDF file. (Impossible to combine several PDF files just in one time) After calling API StartExtractPages(), an extracted document would be generated. It's possible to specify whether to extract different object(s) or information; but when inserting PDF file to the target PDF file, it's only possible to specify whether to insert attachment files to target PDF file or not.

Applicable version	v7.4 or later.
Related APIs	class foxit::pdf::Combintaion
Combine documents options
Sample demo	Not provided in Foxit PDF SDK package yet. APIs of class Combination are easy to understand, so please refer to API reference for APIs of class Combination.
Note	It's possible to combine several PDF files in one time.