Large PDFs should not force you to upload private documents to a random compressor. Batch Compress PDF lets you preview the result first, keeps the originals untouched, and makes the trade-off plain: choose Smart when structure matters, or Flatten when scanned PDFs need the strongest reduction. Choose an input folder and the app finds its PDFs, then writes results into a `compressed` subfolder inside that folder. The original documents are never overwritten. If an output name already exists, Batch Compress PDF keeps both files safely instead of replacing either one; turn on Skip already compressed files when you want repeat runs to leave existing results alone. Choose Flatten for the strongest reduction in most everyday compression jobs, especially scanned or image-heavy PDFs. Flatten creates page-image copies, so it is intentionally clear about the trade-off: searchable text, links, forms, annotations, and accessibility structure are not retained. Choose Smart when the document needs to stay structurally useful. Smart removes unnecessary PDF overhead and recompresses images only when that is useful, while aiming to retain text, vectors, links, forms, annotations, and page geometry. Before committing a batch, compare an Original, Compressed, or Split page preview at the selected setting. The preview makes the quality trade-off visible instead of hiding it behind a percentage claim. Follow progress and per-file results as the folder runs. Every candidate is written temporarily, reopened and validated, then promoted only when it is valid and smaller. A document that cannot be improved is reported unchanged rather than kept as a larger replacement. Batch Compress PDF identifies encrypted, digitally signed, and malformed PDFs before processing and leaves them untouched. Processing, previews, checks, and output validation happen on the PC running the app. No account, upload, analytics, or telemetry is required.