Quick answer: prefer a local browser workflow when the task does not genuinely require a server, and always verify important output.
Put the source files in the right order first
Give the files clear names such as 01-cover.pdf, 02-report.pdf and 03-appendix.pdf. A predictable order prevents an attachment or signature page from appearing in the wrong place.
Open each source briefly and confirm that it is the expected version. Merging is not a substitute for checking duplicates, outdated drafts or missing pages.
Merge locally in the browser
Choose the PDF files in the intended sequence and run the merge. The browser reads their page objects with a locally bundled PDF library, creates a new document and offers it as a download.
Because the work is performed in the tab, there is no upload queue and no remote copy of the selected documents created by InYourTab.com.
Verify the new PDF before deleting anything
Open the merged download and check the page count, first page, last page and every transition between source documents. Forms, bookmarks, digital signatures and unusual embedded content may not behave like ordinary pages.
Keep the original files until the final document has been accepted. A merged PDF is a new file and should not be treated as the only archival copy.
Handle confidential PDFs carefully
Local processing avoids giving the document to a conversion server, but the downloaded result is still a normal file on the device. Save it to an appropriate folder, use device encryption where required and share it only through an approved channel.
Password-protected PDFs may need to be opened or exported by the owner before they can be merged. Do not remove protections from material you are not authorized to use.