Question: I am a senior student, and I have to refer to a lot of documents when writing a thesis, all of which are in PDF format. They are too scattered, ten or twenty files are difficult to save and read, is there any way to combine them into one PDF document?
Answer: You can merge PDF files with the help of free websites. Tools like these allow you to combine documents easily and quickly without registration.
In the next article, the editor will introduce 10 tools for online merging, please be patient and read the detailed tutorial.
10 Free Tools to Merge PDFs Online
Geek Online Merge
Geek PDF Merger is an online tool that can combine PDF files into one file. It is easy to use, and has various functions specially for PDF documents, such as PDF to Word, Excel, PPT, JPG, etc. This also means that with his help, you can convert documents in other formats such as pictures, excel, PPT, etc. into PDF, and merge them into one, which is convenient for sharing and saving.
Geeker PDF file merge 
https://www.geekersoft.cn/pdf-merge-online.html
In addition, this site can split PDF, compress, add watermark, rotate and convert PDF to other editable formats for free.
Online2PDF
Online2PD is an online tool that allows you to combine PDF files into a single PDF file for free. It allows you to select the files to merge and then you can merge them. Apart from merging files into PDF, it can also convert, edit and unlock PDF files. It supports multiple formats like PowerPoint, Publisher, Word, Excel, OpenOffice, PDF, XPS, images, etc. It supports PDF files up to 50MB.
Sejda PDF Merger
Sejda is an online PDF merger software with which you can easily and quickly combine multiple files into one. This allows you to edit the merged file as needed. It allows you to organize multiple files when they are merged together. It has a convenient drag-and-drop feature that can be used to quickly load files to be merged. Furthermore, you can use the site completely free of charge, no prior registration and subscription required.
FoxyUtils Merge PDF
FoxyUtils Merge PDF is a powerful online tool that allows you to merge PDF files into one for free. It's a simple tool that lets you drag and drop files to upload them. After loading the files, it combines multiple files into a single PDF document using a few simple steps. It allows you to combine files into PDF with a maximum limit of 50 MB.
iLovePDF
The well-known online PDF editor iLovePDF website also allows merging documents. To do this, you simply upload the files to the platform and sort them in the desired order. After merging PDFs, you can rearrange and number pages, watermark, rotate, and password protect documents—all for free.
Smallpdf
The Smallpdf website is simple and intuitive to use and provides functions for manipulating PDF files. In addition to combining multiple documents into one, the tool allows you to convert, compress, edit and sign PDFs. To merge files, simply drag them to the corresponding area. Documentation pages can be reordered before generating edits.
Combine PDF
The Combine PDF website works similarly to Smallpdf: up to 20 documents can be combined by dragging and dropping them onto the platform. However, the tool does not allow rearranging the order of pages, only files. The function of Combine PDF also includes converting documents to DOC (Microsoft Word), JPG and PNG formats, and also provides the function of compressing PDF.
PDF Candy
Among the tools for merging PDFs is the PDF Candy website. The site works exactly like any other platform. In terms of additional features, PDF Candy is very similar to iLovePDF. After merging files, you can rearrange, rotate, and number pages, as well as compress and password protect the PDF.
Soda PDF
Of all the options on this list, Soda PDF has the least attractive interface. Still, merging files is no mystery: just upload each file and hit "Merge!" - and unlike other tools, Soda PDF doesn't allow drag-and-drop moves. After rearranging the document order, you can download the final PDF directly from your browser or send it by email.
Flash PDF
Flash Online PDF Editor is another online choice for users who need to merge PDF files. Although the site's features are very similar to those of its competitors, this tool stands out by offering more pre-download processing features. In addition to rearranging the order of pages, Sedja allows you to rotate and view documents in detail. This service is free for documents up to 50 pages or 50 MB.
Professional PDF Editing Software - Desktop Tools
Limitations of Merging PDF Files Online
File size is limited, some support up to 50MB, which makes it difficult to combine large files into PDF. Another downside is that all documents are deleted after merging files is complete or after a few hours of site inactivity.
The Best Software to Merge PDF Files on the Desktop
Apart from using online programs to combine PDF files into one, you can also opt for Geek PDF Editor, which is the best software for merging multiple desktop PDF files into one offline PDF.
Geek PDF Editor Geek PDF Editor-PDF document content editing is easy to handle, editing PDF like editing Word, everything is so simple. https://www.geekersoft.cn/geekersoft-pdf-editor.html Geekersoft PDF Editor is a practical PDF file processing software that can edit, create, convert PDF and OCR files and make them editable. It allows you to change font color or size, insert and resize images, add or delete text or add watermarks to PDF documents. It also allows you to convert PDFs to many other document formats. You can also password protect PDF files to prevent unauthorized access to the files.
