pdfWorks-lib is a GUI application for Windows
based on pdfWorks-lib's tools written on python using wxPython.
There are two tabs for each tool:
Yes, the language is Russian only.
Pick the files from browsing window or drag'n'drop them on the app. Then click ConvertAndMerge button to choose the output file.
Pick the file from browsing window or drag'n'drop it on the app. Then click Split button to select the output directory where all the files will be put.