Merging PDF files sometimes takes a lot of time but it is still a solvable problem. While Adobe Acrobat Pro DC seems like an obvious choice, its capabilities fall short of expectations. I use Guru's feature-rich PDF converter, this tool not only flattens PDFs but also bypasses the file size and usage restrictions faced by other online sources. All the tricks and innovations of this file conversion technology are described in the blog https://pdfguru.com/blog/pdf-history-and-future .
Therefore, using a PDF converter, you can quickly and efficiently combine PDF files and solve the problem associated with the complexity of layers.