To add pages to a PDF online, you can use various web-based services or PDF editing tools. Here are a few options:

1. Smallpdf (www.smallpdf.com): Smallpdf is a popular online platform that offers a wide range of PDF tools, including the ability to add pages to an existing PDF document. Simply visit their website, select the "Add Pages" tool, upload your PDF file, and follow the instructions to add new pages.
2. PDFelement (www.pdfelement.io): PDFelement is a comprehensive PDF editor that also provides an online version. You can visit their website and access their online editor to add pages to your PDF. Upload your file, use the editing tools to insert new pages, and save the modified PDF.
3. Soda PDF (www.sodapdf.com): Soda PDF offers an online PDF editor that allows you to add pages to your PDF document. Visit their website, select the "Edit PDF" option, upload your file, and utilize the editing features to insert new pages where desired.
4. PDF Buddy (www.pdfbuddy.com): PDF Buddy is a simple online tool for editing PDF files. You can upload your PDF, select the "Edit" option, and use the provided tools to add pages to your document. Once done, save the modified PDF file.

These online services typically provide user-friendly interfaces and step-by-step instructions to guide you through the process of adding pages to your PDF. However, please note that some services may have limitations on the number of pages or file sizes for their free versions. Always review the terms of service and any applicable fees before using the tools.

Additionally, ensure that you are uploading your PDF files to reputable and secure platforms, especially when dealing with sensitive information.