You can visit LightPDF to reduce your files size on your phone broswer. There is no need for install an App, truly convenient but not for lots of files.
So, now you can try with several methods, however one the best ways is to get the free version of Adobe Reader. You should have installed the latest version of Adobe Reader that you think is up to date. You can download the free version of the software from here, If the program is not installed or not working properly, you can visit Microsoft. They will provide you the installation instructions of either version. This free version of Adobe Reader can convert PDF, DOC and XPS files. So you can convert the PDFs(To DOC format), DOC files and PSD files into PDF, DOC format. You can do this by using this program. You can also do this, if you know the PDF file format. Furthermore, you can refer to this tutorial for getting PDF file in the proper format from here. That's it. That's all you need.