Download sheet music PDF files to Chromebook.
On Linux terminal, generate a file list:
spzwart@penguin: cd /mnt/chromeos/MyFiles/Downloads/work
$ find /mnt/chromeos/MyFiles/Downloads/work |sort >myfilelist.txt
Open PDFSam basic.
Merge
Specify the file list to identify files for merging, and generate a table of contents from headings.
One file results, with clickable directory at the start of the PDF.