Does a merged PDF keep the author name, software and other hidden details of the original files?

What hidden details does a PDF carry?

Every PDF has an information card you never see on the pages: the document title, the author, sometimes a company name, the program that made it and when it was created. It shows in your reader's document properties window. It often carries the name of the employee who wrote the file, or an old client's name if the file started life as a copy of an earlier template.

What happens to it when you merge

• Title, author, subject and keywords of the original files: not carried over. We tested a file with a title and an author set, and the merged file came out with neither.
• Creating software: the merged file names the PDF library the tool uses instead of your original program.
• Date: the merged file carries the date and time of the merge as its creation date, not the originals' dates.

So Merge PDFs does not leak the old information cards. That does not make the file perfectly clean, though, and this is the detail that matters.

What travels with the pages

Each page is copied with everything on it: text, images, comments and sticky notes, and links. If an old quotation still has a review comment you forgot to delete, or an internal file name printed in its footer, it will be in the merged file. Images on pages are copied as they are too, so a phone photo that was placed with its original data may still carry details such as where it was taken.

A quick check before sending to outsiders

1. Open the merged file and page through it, looking for visible comments or margin notes.
2. If some pages are phone photos, strip their location data with Image metadata inspector and remover before turning them into a PDF and merging.
3. Open the document properties and make sure nothing there bothers you.